Calculators & Converters

401(k) Withdrawal Calculator

Estimate federal tax, state tax, the possible 10% additional tax, withholding, fees, cash received and after-tax value of a US 401(k) withdrawal.

529 Calculator

Project college savings, education costs, a funding gap, and the monthly contribution needed using your own return and inflation assumptions.

Stone to KG Converter

Convert stones (UK weight unit) to kilograms. 1 stone = 6.35029 kg. Handy for medical records, weigh-ins and fitness tracking across systems.

Korean Age Calculator

Compare full age, traditional Korean counting age and year age from your birth date and a reference date locally. The result is arithmetic, not legal advice.

Mahjong Score Calculator

Calculate standard four-player Japanese riichi ron or tsumo payments from selected han, fu, dealer status and a clear mangan-rounding rule.

Darts Score Calculator

Apply one darts visit to a 301 or 501 score. Check remaining points, double-out checkouts and busts without keeping a match record.

Industrial Minutes Calculator

Convert H:MM clock durations to decimal hours and industrial minutes, or reverse industrial minutes to clock time with correct 60-minute carry.

Japanese Era Converter

Convert exact Gregorian dates to Meiji, Taisho, Showa, Heisei or Reiwa dates, or convert a Japanese era date back to Gregorian with boundary checks.

Heart Rate Zone Calculator

Estimate five adult heart rate zones with Tanaka or 220 - age, optionally use heart rate reserve, and understand the limits of age-based targets.

Heat Index Calculator

Estimate the NWS heat index from shade air temperature and relative humidity. Switch between °C and °F and see the matching caution category.

Hectares to Acres Converter

Convert hectares to acres and back with a high-precision factor for farming, surveying, forestry and real-estate listings.

Horsepower to Watts Converter

Convert mechanical, metric, electrical and boiler horsepower to watts and kilowatts with their distinct factors for engines, reference tables and steam boilers.

Acreage Calculator

Calculate acreage from multiple rectangles, triangles, trapezoids and circles. Add or subtract sections and review exact acre and hectare conversions.

Hypotenuse Calculator

Find the hypotenuse of a right triangle from its two legs using c = sqrt(a^2 + b^2). Get the hypotenuse plus area, perimeter and both acute angles instantly.

Time Value of Money Calculator

Solve for present value, future value, payment, interest rate or periods with regular cash flows, payment timing and one shared frequency.

VA Combined Rating Calculator

Estimate a VA combined disability rating with 38 CFR 4.25 whole-person math and the 4.26 bilateral factor, including the favorable exception.

Water Heater Size Calculator

Size a storage water heater by First Hour Rating or estimate tankless flow and heat load from simultaneous demand and temperature rise.

Well Pump Size Calculator

Estimate a residential well pump duty point from peak flow, pumping water level, pressure and friction, then check the well-yield shortfall.

Snow Day Heuristic Calculator

Combine manually entered snow, ice, temperature, wind and local context into an uncalibrated disruption score. Not a forecast or closure prediction.

Sourdough Hydration Calculator

Calculate true sourdough hydration from final-mix flour, water and starter, then find the water or flour adjustment for a target percentage.

Speaker Crossover Calculator

Estimate ideal first- or second-order passive two-way crossover inductors and capacitors from frequency and driver impedance.

Speaker Impedance Calculator

Calculate the nominal load of identical passive speakers wired in series, parallel or balanced series-parallel, then compare an amplifier minimum.

System of Equations Calculator

Numerically classify 2x2 and 3x3 linear systems with RREF, a 1e-10 tolerance, ranks, determinant and residual checks.

Taxable Social Security Benefits Calculator

Estimate the 2025 federal taxable portion of Social Security benefits with the latest final IRS worksheet, verified July 2026, thresholds and an audit trail.

Rounding Calculator

Round exact decimal values from 12 decimal places to trillions. Compare half-even, half-away, ceiling, floor and four other modes.

RREF Calculator

Find the reduced row echelon form of a numeric matrix. See row operations, rank, nullity, pivot columns, and free columns for matrices up to 8 × 8.

Sand Calculator

Estimate sand for rectangular, circular, triangular or known areas. Calculate finished and purchase volume, weight, whole bags and material cost.

SAT Score Calculator

Add official SAT Reading and Writing and Math scores to compare test dates, calculate a superscore and measure the gap to a planning target.

Siding Calculator

Estimate siding from wall, gable and opening measurements, add waste, and calculate trade squares and packages in imperial or metric units.

Ski Size Calculator

Estimate an adult resort ski length band from height, discipline, ability, relative weight and preferred feel, then check the exact model chart.

Snowboard Size Calculator

Estimate an adult snowboard length range and width category from weight, height, boot size, ability and riding style, then check the exact model chart.

RAID Calculator

Compare RAID 0, 1, 5, 6, 10, 50 and 60 capacity. Model mixed drive sizes, parity spans, hot spares, TB versus TiB and average drive cost.

Rain Barrel Calculator

Estimate roof rainwater yield, actual barrel capture, overflow, storage fill and optional no-more-rain usage coverage for one rainfall event.

Ramp Calculator

Estimate ramp run, surface length, slope, angle, landing count and material area from rise, target run ratio, width, landing size and waste.

Rent Affordability Calculator

Estimate an affordable monthly rent from household income, tenant-paid utilities and a chosen housing-cost percentage. Includes the common 30% benchmark.

Resin Calculator

Estimate epoxy resin for rectangular, round or known-area pours, add an allowance, and split the mixed total by a volume or weight ratio.

Roof Truss Calculator

Estimate roof truss positions, even bay spacing, gable rise and roof-line lengths from building length, span, pitch and horizontal overhang.

Pond Liner Calculator

Calculate minimum pond liner length, width and area from planned dimensions or measured excavation profiles, with a per-side edge allowance.

Pool Pump Size Calculator

Calculate required pool circulation flow from volume and turnover time, or check turnover from an actual flow rate, in gallons/GPM or m³/m³/h.

Pool Salt Calculator

Calculate pool salt from current and target salinity in ppm. Get kilograms, pounds, bag estimates or a cautious dilution estimate when salt is high.

Quilt Backing Calculator

Calculate quilt backing size, panels, seams, cut lengths and fabric yardage for vertical or horizontal layouts, including optional shrinkage.

Options Profit Calculator

Calculate listed option payoff at expiration for long calls, long puts, short calls and short puts using strike, premium, contracts, multiplier and fees.

Partial Derivative Calculator

Differentiate multivariable polynomial terms with respect to x, y or z, then optionally evaluate the partial derivative at a point.

Freight Class Calculator

Calculate an LTL density-class estimate from identical unit dimensions and weight. Verify the NMFC item and carrier requirements before shipping.

Life Insurance Calculator

Estimate a life insurance coverage gap from obligations, income replacement, education costs, liquid assets, and existing coverage.

Mortgage Recast Calculator

Estimate your new principal-and-interest payment after a mortgage recast, plus monthly savings, remaining interest and fee-adjusted benefit.

Odds Ratio Calculator

Calculate an odds ratio from a 2×2 contingency table and estimate its log-Wald 95% confidence interval with transparent formulas and examples.

Hay Calculator

Plan livestock hay inventory from animal weight, hay dry-matter intake, feeding days, moisture, waste and measured bale weight.

Helix Length Calculator

Calculate circular helix centerline length from radius or diameter, axial pitch, and turns or total rise. See length per turn, total rise and helix angle.

Home Sale Calculator

Estimate seller net proceeds after mortgage payoff, commissions, closing costs, concessions, repairs, taxes, liens and other sale expenses.

Horse Weight Calculator

Estimate a mature horse, yearling or weanling’s weight from heart girth and body length in centimetres or inches.

Kiln Firing Cost Calculator

Estimate an electric pottery kiln firing from measured kWh or rated power, then add accessories and overhead for per-piece and monthly costs.

Knitting Gauge Calculator

Convert a measured knitting swatch into stitch and row gauge, then estimate cast-on stitches and rows for a finished size with repeat-aware rounding.

French Drain Calculator

Estimate French drain excavation, aggregate after pipe displacement, purchase allowances, fabric, cap space, pipe length, fall and optional stone mass.

Air Changes per Hour Calculator

Calculate air changes per hour from room dimensions and airflow, or find the airflow needed for your target ACH in CFM or m³/h.

Circle Skirt Calculator

Calculate waist and hem radii for quarter, half, three-quarter or full circle skirts, including ease and sewing allowances.

Conduit Fill Calculator

Calculate conduit fill for one group of copper THHN/THWN-2 wires from 14 AWG to 4/0, with permitted area, remaining area and maximum count.

Crochet Blanket Size Calculator

Turn a measured crochet swatch and editable blanket size into repeat-aware working stitches, foundation chains, rows and finished dimensions.

Dehumidifier Size Calculator

Estimate portable dehumidifier capacity from floor area and dampness using current ENERGY STAR guidance, with results in pints and liters per day.

Dog Crate Size Calculator

Calculate minimum internal dog crate dimensions for home use or estimate an IATA CR1 air-travel container from body measurements.

Duct Size Calculator

Estimate round or rectangular duct dimensions from airflow and target velocity, or check air velocity through an existing duct in imperial or metric units.

Fabric Yardage Calculator

Estimate fabric for identical rectangular pieces using usable width, quantity, rotation, pattern repeat, shrinkage and waste allowances.

Filament Weight Calculator

Convert 3D printing filament length and mass, estimate material left from gross and tare spool weights, and calculate optional material value.

Board and Batten Calculator

Plan interior board-and-batten spacing, center marks and vertical stock boards from your wall, target clear gap, trim size, kerf and spare allowance.

CPU vs GPU Bottleneck Calculator

Compare CPU and GPU frame times from the same game scene, estimate the FPS ceiling, apply a tolerance and understand what the result can and cannot prove.

Budget at Completion Calculator

Roll allocated and undistributed budget into BAC, keep management reserve separate, and reconcile a reported BAC privately in your browser.

Credit Card Interest Calculator

Estimate one credit card billing cycle using APR, inclusive dates, an opening balance, and dated purchases, payments, or credits.

Crochet Increase Calculator

Place crochet increases or decreases across a row or round from a change count or target count, with edge reserves and exact source-stitch positions.

Curtain Size Calculator

Calculate curtain width, fullness, panel count and drop from rod or window measurements, with optional ready-made panel and pack checks.

FERS Retirement Calculator

Estimate a US FERS basic annuity from high-3 salary, creditable service, retirement age, MRA+10 timing and a survivor election.

Attic Fan Calculator

Compare PNNL low-flow and HVI powered attic ventilator references, soffit intake NFA, and separate 1:150 and 1:300 passive vent figures.

Bike Size Calculator

Screen adult road, mountain and hybrid bike standover height from cycling inseam, frame style and optional candidate geometry before checking the model chart.

Port Length Calculator

Estimate round or slot speaker-port length from net box volume, target tuning frequency, clear port dimensions and port count in metric or imperial units.

Reverb Time Calculator

Estimate a room's RT60 from its dimensions and floor, ceiling and wall absorption using the Sabine and Eyring reverberation formulas.

Room Mode Calculator

Calculate rectangular-room resonance frequencies, inspect axial, tangential and oblique modes, and find closely spaced low-frequency modes.

Sandbag Calculator

Estimate bags, reserve, sand-fill weight and footprint for a temporary barrier using the named USACE 2022 1-to-5-foot planning tiers.

Subwoofer Box Calculator

Calculate gross and net subwoofer enclosure volume, account for driver, bracing and port displacement, or solve one rectangular box dimension.

Yarn Yardage Calculator

Estimate yarn left from label length and weight, or turn a known project length plus reserve into whole skeins. Supports metres, yards, grams and ounces.

Gold Calculator

Estimate gold melt value from weight, karat or purity percent, spot price per troy ounce and dealer fee. No live prices or uploads.

Graphing Calculator

Plot functions of x, inspect the x/y table and adjust the viewing window with a fast browser-based graphing calculator.

Julian Day Converter

Convert Gregorian UTC dates, Julian Date, Modified Julian Date and Unix seconds with millisecond precision, offset handling and copy-ready values.

2-Stroke Oil Mix Calculator

Calculate two-stroke oil from petrol or gasoline, or work backward from oil on hand. Supports metric, US and Imperial units and custom ratios.

Audiobook Calculator

Calculate remaining audiobook time at any playback speed, track progress, plan daily listening and find the speed needed to meet a deadline.

Eigenvalue Calculator

Find the eigenvalues, trace, determinant, discriminant and real eigenvectors of a 2x2 matrix with a clear characteristic-polynomial breakdown.

Factoring Calculator

Factor quadratics ax^2 + bx + c and extract integer GCFs. Shows factored form, ac-method pair, roots and step-by-step grouping notes.

Final Exam Calculator

Calculate the score you need on a weighted final exam to reach your desired course grade, then check the outcome for an expected exam score.

Chemical Equation Balancer

Balance chemical equations with integer coefficients. Enter reactants and products, then check atoms on both sides with a per-element table.

Chi-Square Calculator

Calculate chi-square tests from observed and expected counts or contingency tables, with df, p-value, Cramers V and expected-count checks.

Clock Out Time Calculator

Calculate your clock-out time from your clock-in time, required paid hours and unpaid breaks. Handles overnight shifts and shows 12- and 24-hour time.

Compost Calculator

Calculate compost volume for a garden bed, adjust for settling, compare bags with bulk cubic yards and estimate greens versus browns.

CPM Calculator

Calculate CPM from spend and impressions, then compare CPC, CTR, CPA, ROAS, revenue per mille, profit and margin for an ad campaign.

A1C Calculator

Convert HbA1c between NGSP % and IFCC mmol/mol, calculate eAG in mg/dL or mmol/L, or estimate A1C from eAG with safety-focused guidance.

Bra Size Calculator

Estimate independent US, UK and EU starting bra sizes from snug underbust and full-bust measurements, privately in your browser.

Catalytic Converter Replacement Cost Calculator

Estimate catalytic converter replacement cost from parts, labor, diagnostics, fees and tax, with an itemized total and practical planning range.

Car Lease Calculator

Calculate a car lease monthly payment using capitalized cost, residual value, money factor, term and sales tax. The breakdown shows depreciation, the finance charge, the residual value and the equivalent APR.

Carpet Calculator

Estimate carpet area in square yards, square feet and square metres. Add your own waste allowance and, optionally, a price in the site currency.

Cash Back Calculator

Estimate the cash back you earn on your credit card each month and year. Enter your monthly spend, cash back rate and annual fee to see your net rewards.

Cat Age Calculator

Convert your cat's age to human years using vet-adjusted mapping. Accounts for faster aging in kittens and slower later-life progression.

Cat Food Calculator

Calculate daily calories and food portions for your cat by weight, age and activity level. Works for dry, wet and mixed feeding.

Celsius to Kelvin Converter

Convert Celsius to Kelvin by adding 273.15. Used in chemistry, physics and engineering, with key reference points for science and photography.

Capacitive Reactance Calculator

Calculate capacitive reactance Xc from frequency and capacitance. Enter frequency in Hz and capacitance in µF and get the reactance in ohms (Ω) instantly.

Capacitor Charge & Energy Calculator

Calculate the charge and stored energy of a capacitor from its capacitance and voltage using Q = C·V and E = ½·C·V², with readable mC/µC and mJ/µJ results.

Capital Gains Tax Calculator

Estimate US federal capital gains tax on stocks, crypto, real estate and other assets. Short vs long-term holding, income bracket aware.

Cap Rate Calculator

Calculate the capitalization rate of any rental property from its purchase price, gross income and operating expenses. See the cap rate %, net operating income and monthly NOI instantly.

Money Counter

Count cash by US bills, loose coins and standard coin rolls. Enter each denomination count to get bill totals, coin value, pieces and a grand total.

Calories Burned Calculator

Estimate the calories you burn during any workout from your body weight, the activity and how long you did it, using science-based MET values.

Calories to Joules Converter

Convert calories (kcal) to joules and kilojoules using the food calorie factor of 4,184 joules per kilocalorie.

Laplace Transform Calculator

Find common Laplace transforms for constants, powers, exponentials, sine and cosine terms with a clear formula, convergence region and worked example.

Long Division Calculator

Divide whole numbers with long-division steps. Get quotient, remainder, decimal expansion and a digit-by-digit table for checking schoolwork.

Buoyancy Calculator

Calculate buoyant force with the Archimedes formula F = ρ·V·g. Enter fluid density and submerged volume to get the upward force in newtons and the mass of fluid displaced in kilograms.

Butter Cups to Grams Converter

Convert butter from US cups to grams: 1 cup = 227 g, 1/2 cup = 113 g. Plus ounces, tablespoons and stick equivalents for precise baking.

Butter Sticks to Grams Converter

Convert US butter sticks to grams. 1 stick = 113 g = 1/2 cup = 8 tbsp. Handles fractional sticks and half-sticks with exact equivalents.

Caffeine Half-Life Calculator

Estimate how much caffeine remains in your body hour by hour from your dose and personal half-life, and see when it drops below a chosen level.

CAGR Calculator

Calculate the compound annual growth rate (CAGR) of an investment from its beginning value, ending value and holding period. See total growth and the growth multiple too.

Calendar Date Series Generator

Generate a list of dates from a start date and an ISO 8601 interval (every day, week, 2 weeks, month or year), with weekday names and up to 200 entries.

Break-Even Calculator

Calculate the units or revenue needed to cover fixed costs based on price, variable cost and contribution margin.

Brick Calculator

Work out how many bricks and bags of mortar you need for a wall. Enter length, height and brick type, add a waste factor, and get an instant material count.

BTC to USD Converter

Convert Bitcoin to US dollars at the current live rate. The rate is cached for five minutes and can be refreshed with one click.

BTU Calculator

Estimate the BTU per hour and the AC size in tons you need to cool a room. Enter room dimensions, ceiling height, sun exposure and occupants for an instant result.

Bowling Score Calculator

Calculate your ten-pin bowling score with full strike and spare bonuses. Enter your rolls using X, / and - and get the exact total plus a frame-by-frame breakdown.

Boyle's Law Calculator

Solve Boyle's law P₁V₁ = P₂V₂ for the final volume V₂ instantly. Enter the initial pressure and volume plus the new pressure, and read the answer right away.

Bra Size Converter

Convert bra sizes between UK, US, EU, French/Belgian and Australian/New Zealand systems with the standard band and cup conversions.

Binomial Probability Calculator

Compute exact, cumulative and tail probabilities for a binomial distribution. Enter n trials, p success rate and k successes.

Biweekly Mortgage Calculator

Compare biweekly mortgage payments vs monthly. See years shaved off the loan and total interest saved with true biweekly amortization.

Board Foot Calculator

Calculate board feet for any lumber from thickness, width and length, multiply by quantity, and add a price per board foot to get the total cost for your order.

Bond Yield Calculator

Calculate current yield and yield to maturity for a bond from its face value, coupon rate, market price and remaining term.

Batting Average Calculator

Calculate a baseball or softball batting average from hits and at-bats. Enter the numbers and get the standard three-decimal AVG (like .300) instantly.

Bar to PSI Converter

Convert pressure from bar to pounds per square inch (psi) and kilopascals (kPa). 1 bar = 14.5038 psi exactly.

Battery Life Calculator

Estimate how long a battery will last from its capacity in mAh, the load current in mA and a discharge efficiency factor. Get runtime in hours, days and minutes.

Baby Percentile Calculator

Enter your baby's age, sex and weight to see an approximate weight percentile band and the reference range for that age, from birth to 24 months.

Baluster Calculator

Enter your rail span, baluster width and code maximum gap to get the exact number of balusters you need and the even spacing between each spindle, with no gap wider than code.

Asphalt Calculator

Estimate how much asphalt you need for a driveway, lot or road. Enter length, width and thickness to get tons, square footage, cubic yards and total cost.

ATM to PSI Converter

Convert atmospheric pressure from atmospheres (atm) to pounds per square inch (psi) and bar with the exact factor 1 atm = 14.6959 psi.

Auto Loan Calculator

Calculate the monthly payment, total interest and total paid on a new or used car loan. Include down payment, trade-in and sales tax.

Aquarium Size Calculator

Calculate aquarium volume in US gallons and litres from the inner tank dimensions in inches, plus the filled water weight in pounds and kilograms.

Arc Length Calculator

Calculate the arc length of a circle from radius and central angle in degrees or radians, along with the chord length and sector area.

Arithmetic Sequence Calculator

Find the nth term and sum of an arithmetic sequence from the first term, common difference and number of terms. See a sequence preview instantly, free.

Army Body Fat Calculator

Estimate body fat percentage using the US Army tape test (AR 600-9): height, neck and waist for men, plus hip for women.

Arrhenius Equation Calculator

Calculate the reaction rate constant k from the pre-exponential factor A, activation energy Ea (kJ/mol) and temperature T (K) using the Arrhenius equation, instantly in your browser.

Annuity Calculator

Calculate the payment per period, total paid and total interest for an annuity from a lump sum (principal), annual rate, term and payment frequency. Works for loan amortization and payouts from a lump sum.

ANOVA Calculator

Perform one-way ANOVA on two or more groups to test whether their means differ significantly. Reports the F-statistic, degrees of freedom, mean squares and sums of squares.

Antilog Calculator

Compute the antilogarithm (inverse log) for base 10, e, 2 or a custom base. Enter the exponent and instantly get b raised to that power, with the base shown.

APR Calculator

Calculate the real APR on a loan including origination fees, points and closing costs, the comparable number lenders must disclose.

APY Calculator

Convert a nominal interest rate to effective APY given compounding frequency, and find the APY for savings accounts, CDs and high-yield accounts.

Allowance Calculator

Calculate an age-appropriate kids allowance using the "dollar per year" rule and chore-based variants, with annual totals for budgeting.

Amp-Hour Calculator

Work out battery runtime and stored energy from amp-hours, voltage and load current. Get runtime in hours and minutes plus energy in watt-hours and kilowatt-hours.

Angular Velocity Calculator

Calculate angular velocity (rad/s), frequency (Hz) and RPM from linear velocity and radius using ω = v / r. Instant, accurate results for any rotating object.

Anion Gap Calculator

Calculate the serum anion gap from sodium, chloride and bicarbonate in mEq/L. Shows the result with a worked example and reference ranges, for educational use only.

Area Converter

Convert between common area units: m², km², ft², yd², in², cm², mm², acres and hectares. With precise factors and quick-reference values.

ARM Mortgage Calculator

See the monthly payment on an adjustable-rate mortgage during the fixed intro period and after the first reset, with the balance at reset.

Boat Loan Calculator

Estimate monthly payments and total interest for a boat loan. Enter the price, down payment, rate and term to see the monthly payment, total paid and interest for common marine terms of 5 to 20 years.

Budget Calculator

List your monthly income and expenses by category to see your total spending, what remains each month and how much of your income goes out.

Business Loan Calculator

Calculate the monthly payment, total interest and fees for a fixed-rate business term loan from the loan amount, annual rate, term and origination fees.

Cash-Out Refinance Calculator

Calculate a cash-out refinance: the new loan amount, loan-to-value ratio, monthly payment, total interest and the cash you receive, based on your inputs.

CM to Inches Converter

Convert centimetres to inches and feet using the exact 2.54 cm/inch definition.

Amortization Calculator

Build a monthly amortization schedule for a fixed-rate loan, showing principal, interest and remaining balance for every payment, plus total interest and total paid.

Car Loan Calculator

Estimate a car loan payment from the amount financed, APR and term. See the monthly payment, total paid and total interest to compare the full cost of each offer.

Compound Interest Calculator

Project savings or investment growth with compound interest. Model an opening balance, regular contributions, annual rate, compounding frequency and time horizon.

Dividend Calculator

Estimate annual dividend income, current dividend yield and reinvested growth from shares, price, dividend per share and dividend growth assumptions.

Investment Calculator

Estimate future investment value from a starting balance, monthly contributions, annual return and time horizon, with inflation-aware planning notes.

ABV Calculator

Enter original gravity (OG) and final gravity (FG) to calculate ABV, ABW, apparent attenuation and calories per 355 ml / 12 fl oz serving.

Acceleration Calculator

Calculate acceleration from initial velocity, final velocity and time using a = (v − u) / t. Shows result in m/s², equivalent g-force, and the change in velocity.

Acres to Square Feet Converter

Convert acres to square feet and back with the exact factor 1 acre = 43,560 sq ft. Useful for land listings, deeds, surveys and site plans.

Adult Height Predictor Calculator

Get a rough mid-parental estimate of a child's adult height from biological parent heights. It is not a diagnosis or a personal growth forecast.

10K Pace Calculator

Calculate the pace per kilometer and per mile you need for a 10 km target, with 5K split timing and matching treadmill speeds in km/h and mph.

401k Calculator

Project your 401(k) balance from salary, age, contribution percent, employer match and expected return, with 2026 IRS limits and a year-by-year breakdown.

5K Pace Calculator

Work out the pace per km and per mile for a 5K target time up to 24 hours, plus 1K split times you can program into a watch.

Acres to Hectares Converter

Convert acres to hectares with the exact factor 1 acre = 0.40468564224 ha, plus reverse conversion notes and practical land-size examples.

Pythagorean Theorem Calculator

Solve any side of a right triangle with a² + b² = c². Enter two sides to get the missing leg or hypotenuse, plus the triangle angles.

Simple Interest Calculator

Compute simple interest with the P × r × t formula. Enter principal, annual rate and time to see interest earned and final balance.

Square Root Calculator

Compute square roots for positive numbers, zero and negatives. Get a decimal approximation, simplified radical form for whole-number inputs and clear notes on perfect squares and complex roots.

Feet to Inches Converter

Convert decimal feet to inches with the exact factor of 12 and a centimeter cross-check for plans, product dimensions, heights and imported measurements.

Fuel Cost Calculator

Estimate fuel cost for a drive from distance, fuel economy and pump price. Use MPG with gallons, km/L with litres, or convert L/100 km before calculating.

Military Time Converter

Convert 2:30 PM to 14:30 or 14:30 to 2:30 PM. Clear 12-hour and 24-hour time conversion for schedules, aviation, healthcare, logs and travel.

Moon Sign Calculator

Estimate which zodiac sign the Moon was in on your birth date and learn what Moon signs mean in a Western natal chart.

Numerology Calculator

Calculate name-based numerology numbers with Pythagorean or Chaldean letter values: expression, soul urge and personality.

Ratio Calculator

Enter any three values in a:b = c:d to find the missing term. Whole-number a:b ratios are also reduced to lowest terms.

Rising Sign Calculator

Estimate your rising sign from birth date and birth time. This quick astrology calculator uses a simple two-hour block method, not a full birth chart.

Running Pace Calculator

Enter distance and finish time to calculate pace per km, pace per mile, average speed and projected 5K, 10K, half marathon and marathon finish times.

Age Difference Calculator

Calculate the exact age gap between two birth dates in years, months and days, with total months, weeks and days.

Tip Split Calculator

Split a restaurant bill by bill amount, tip percentage and group size, with tip, total and per-person amounts shown instantly.

USD to EUR Converter

Convert US dollars to euros with the exchange rate you enter. Handy for travel budgets, online shopping, invoices and quick estimates.

Triple Integral Calculator

Approximate definite triple integrals over numeric x, y and z bounds with the midpoint rule in your browser.

HELOC Payment Calculator

Estimate interest-only draw payments and fully amortized HELOC repayment payments from a balance, current rate, and remaining periods.

Height Feet & Inches to CM Converter

Convert a height in feet and inches to centimetres and metres. Useful for medical forms, passports and fitness apps.

Inches to Feet Converter

Convert inches to decimal feet and yards instantly. Useful for construction, DIY, spreadsheet estimates and imperial measurement work.

Name Numerology Calculator

Calculate your destiny number and expression number from your full name using Pythagorean numerology, with a personality reading.

Aspect Ratio Calculator

Enter a width and height to find the aspect ratio and its decimal value, then add a new width or height to get the matching dimension.

Cholesterol Ratio Calculator

Enter lipid panel values in mg/dL or mmol/L and review total/HDL, LDL/HDL and triglyceride/HDL ratios with cautious context.

Waist to Hip Ratio Calculator

Calculate waist-to-hip ratio from matching waist and hip measurements, then compare your WHR with sex-specific screening bands. Private and no login required.

BMI Calculator

Calculate body mass index from height and weight. Shows WHO category, healthy-weight range and limitations of BMI.

Calorie Calculator

Estimate daily calorie needs for your goal using Mifflin-St Jeor BMR and activity factors. Includes deficit and surplus targets.

GPA Calculator

Calculate grade point average from letter grades and credit hours. Supports US 4.0 and 5.0 honors scales with the standard A/B/C/D letter table.

Paycheck Calculator

Estimate take-home pay from gross pay and the percentage deductions you enter. Calculations run locally in your browser.

Age Calculator

Calculate exact age in years, months and days from a birth date, plus total days, hours and the next birthday countdown.

Concrete Calculator

Calculate how much concrete you need for slabs, footings, columns and walls. Get cubic yards, bag counts and material cost estimates.

Inflation Calculator

Estimate a hypothetical future cost and present buying power from an amount, an annual rate and a number of years. Runs locally in your browser.

Scientific Calculator

Evaluate supported real-number expressions with trig, logs, powers and parentheses locally in your browser.

TDEE Calculator

Estimate BMR and daily TDEE with the Mifflin-St Jeor equation and a selected activity factor.

Tip Calculator

Work out the tip amount and total bill from any subtotal and tip percentage with optional tax handling.

Fraction Calculator

Compute sums, differences, products and quotients of fractions. Results appear in lowest terms, with the decimal and mixed-number forms shown for checking.

World Clock

See the current time in multiple cities side by side with daylight-saving adjustments. Useful for distributed teams and travel.

Blood Alcohol Content Calculator

Estimate BAC using the Widmark formula based on drinks, body weight, sex and time since first drink. Educational only, not legal advice.

Ovulation Calculator

Estimate your ovulation date and fertile window based on the first day of your last period and average cycle length.

BMR Calculator

Estimate your basal metabolic rate, the calories you burn at complete rest. Uses the Mifflin-St Jeor equation, the current clinical standard.

CD Calculator

Calculate the interest and final balance on a Certificate of Deposit. Handles compounding frequency and early withdrawal penalties.

Time Zone Converter

Convert a time between any two time zones, with daylight-saving shifts applied automatically.

EUR to USD Converter

Convert Euros to US Dollars with your chosen EUR/USD rate. Enter the current rate manually, compare scenarios and copy the result.

Percentage Change Calculator

Measure how much a number went up or down in percent. Handles growth, decline, year-over-year, and signed change with the exact formula shown.

Roth IRA Calculator

Estimate Roth IRA growth from annual contributions, expected return and years to retirement. Shows contributions vs growth, with after-tax equivalence.

Time Duration Calculator

Calculate the duration between two times in HH:MM, decimal hours, minutes and seconds.

Work Hours Calculator

Calculate total work hours from start and end times with breaks and overtime, perfect for timesheets and contractor invoices.

Integral Calculator

Approximate definite integrals for built-in functions such as e^x, sin(x), x², x³, √x, 1/x and ln(x) using composite Simpson's rule.

Macro Calculator

Turn a daily calorie target and macro percentages into grams of protein, carbs and fat. Check balanced, high-protein, muscle-gain and lower-carb splits.

Sales Tax Calculator

Calculate tax on a tax-exclusive amount, or extract the tax included in a gross price. Works with sales tax, VAT, GST and custom rates.

Celsius to Fahrenheit Converter

Convert Celsius to Fahrenheit with the standard formula, quick weather references, oven settings, body-temperature context and Kelvin.

One Rep Max Calculator

Estimate your one-rep max (1RM) from weight lifted and reps completed using Epley, Brzycki and Lander formulas.

Polynomial Derivative Calculator

Differentiate polynomial expressions such as 3x^3 + 2x^2 - 5x + 7 and see how constants, coefficients and powers become f'(x).

Standard Deviation Calculator

Compute mean, variance, and standard deviation (sample n-1 or population n) for any dataset. Shows coefficient of variation and z-scores.

Dog Age Calculator

Convert your dog's age to human years using modern veterinary research. Breed-size aware: small, medium and large dogs age differently.

GBP to USD Converter

Convert British pounds to US dollars at the current exchange rate. See the mid-market rate, plus how banks and card networks apply their margin.

HELOC Calculator

Estimate gross HELOC capacity from home value, first mortgage, other secured liens and a planning CLTV limit before lender underwriting.

KM to Miles Converter

Convert kilometres to statute miles with the exact 0.621371 factor. Useful for running splits, road-trip planning and imported navigation data.

Mulch Calculator

Calculate mulch volume from bed length, width and depth. Get cubic feet, cubic yards, 2 cu ft bag equivalents and bulk versus bag cost.

Paint Calculator

Estimate wall and ceiling paint from room dimensions, coats, coverage rate and price per gallon, with metric conversion guidance for litre-based paint labels.

Percent Calculator

Calculate a percent of a value, add or subtract a percent, or find the original value behind a percentage. Enter two numbers and see every formula.

Period Calculator

Estimate the start and end dates of your next 6 periods from your last period, cycle length and bleeding duration. Educational tool, not medical advice.

Pregnancy Due Date Calculator

Estimate your baby's due date from the first day of your last period or a known conception date. Uses Naegele's rule, cycle-length adjustment and standard obstetric timing.

Savings Calculator

Project the future value of your savings from a starting balance, regular deposits, an annual rate and a chosen term, with monthly, annual or custom compounding.

Take-Home Pay Calculator

Estimate US take-home pay after federal income tax, FICA, state and local taxes, plus common payroll deductions.

Unit Converter

Convert metric, US customary and imperial units across length, weight, volume, time, speed and area. Uses precise base factors in one simple converter.

Yen to USD Converter

Convert Japanese yen (JPY) to US dollars with a manual USD-per-JPY rate. Use the default estimate or paste your current card, bank or FX rate.

Body Fat Percentage Calculator

Estimate body fat percentage from neck, waist, hip and height measurements. Uses the classic US Navy tape formula for trend tracking, not diagnosis.

Home Affordability Calculator

Estimate a realistic home price from income, debts, down payment, rate, term and monthly tax plus insurance costs.

Social Security Calculator

Estimate a US Social Security retirement benefit from your PIA and claiming age. Compare monthly and annual amounts at 62, FRA 67 and 70.

Triangle Calculator

Enter three side lengths to check whether they form a valid triangle, then calculate the type, area, perimeter and all three angles.

Business Days Calculator

Count business days in an inclusive date range. Shows Monday-Friday workdays, Saturday/Sunday weekend days, total calendar days and work-week equivalent.

Closing Cost Calculator

Estimate US home purchase or refinance closing costs from lender fees, title insurance, appraisal, inspection, recording, prepaid taxes, HOA and other line items.

Discount Calculator

Calculate the final price and savings from an original price and a percent-off discount. Useful for sale tags, coupons and quick checkout checks.

eGFR Calculator

Estimate eGFR from serum creatinine, age and sex using the race-free 2021 CKD-EPI creatinine equation. Results in mL/min/1.73 m².

N·m to ft-lb Converter

Convert Newton-meter torque values to ft-lb, lb-ft and in-lb for workshop manuals, wheel nuts, bicycle bolts and mechanical jobs.

Fahrenheit to Celsius Converter

Convert Fahrenheit temperatures to Celsius with the exact formula, Kelvin output and common reference points for weather, cooking and health.

USD to GBP Converter

Convert US dollars to British pounds at the latest reference rate. Useful for UK shopping, travel, invoices and quick price checks.

Miles to KM Converter

Convert miles to kilometers with exact factor (1 mi = 1.609344 km). Includes a common-distance reference table and mental-math shortcuts.

Savings Goal Calculator

Work out how much to save each month to reach a target amount by a specific date, with an assumed interest rate.

Cooking Unit Converter

Convert cooking volume units including teaspoons, tablespoons, fluid ounces, cups, pints, quarts, gallons, millilitres and litres.