Unit Converter
Convert the everyday units people mix most often: meters and feet, kilograms and pounds, liters and US gallons, seconds and hours, km/h and mph, square meters and acres. Choose a category, enter a value, then switch source and target units in one click. The converter stores each unit against a single base unit so repeated conversions stay stable.
How to convert units
-
1
Choose a category
Pick length, weight, volume, time, speed or area so the tool loads the right unit list.
-
2
Enter the value
Use decimals or scientific notation such as 12.5, 1e6 or 0.0254.
-
3
Pick source and target units
Select the unit you have and the unit you need, or use swap to reverse them instantly.
-
4
Read the converted value
The result updates as you type and trims trailing zeros to keep the answer readable.
Conversion factors used by this tool
Every category has one base unit. Your input is first converted to that base, then divided by the target unit factor. That avoids extra rounding from chained conversions.
Length (base: meter)
| Unit | Factor to meter |
|---|---|
| meter | 1 |
| kilometer | 1,000 |
| centimeter | 0.01 |
| millimeter | 0.001 |
| inch | 0.0254 (exact) |
| foot | 0.3048 (exact) |
| yard | 0.9144 (exact) |
| mile | 1,609.344 (exact) |
Weight / mass (base: gram)
| Unit | Factor to gram |
|---|---|
| gram | 1 |
| kilogram | 1,000 |
| milligram | 0.001 |
| metric ton / tonne | 1,000,000 |
| ounce (avoirdupois) | 28.3495 |
| pound (avoirdupois) | 453.592 |
| stone | 6,350.29 |
Volume (base: liter)
| Unit | Factor to liter |
|---|---|
| liter | 1 |
| milliliter | 0.001 |
| cubic meter | 1,000 |
| US gallon | 3.78541 |
| US quart | 0.946353 |
| US pint | 0.473176 |
| US cup | 0.236588 |
| US fluid ounce | 0.0295735 |
Time (base: second)
| Unit | Factor to second |
|---|---|
| second | 1 |
| millisecond | 0.001 |
| minute | 60 |
| hour | 3,600 |
| day | 86,400 |
| week | 604,800 |
| Julian year | 31,557,600 |
Speed (base: meter per second)
| Unit | Factor to m/s |
|---|---|
| m/s | 1 |
| km/h | 0.277778 |
| mph | 0.44704 |
| knot | 0.514444 |
| ft/s | 0.3048 |
Area (base: square meter)
| Unit | Factor to m² |
|---|---|
| m² | 1 |
| km² | 1,000,000 |
| cm² | 0.0001 |
| hectare | 10,000 |
| ft² | 0.092903 |
| acre | 4,046.86 |
Notes on common traps
- US and UK gallons are different. This converter uses US customary volume units. If a UK recipe or engineering spec says imperial gallon, do not treat it as a US gallon.
- Temperature needs a separate converter. Celsius, Fahrenheit and kelvin require offsets, not just multiplication factors.
- Unit symbols stay universal. Symbols such as m, kg, L, ft, mph and m² are kept as symbols so formulas and labels remain unambiguous across languages.
Frequently Asked Questions
Volume units use the US customary system: gallon, quart, pint, cup and fluid ounce. Length and weight units such as inch, foot and pound are the same in modern US and UK usage.
The international foot has been defined as exactly 0.3048 m since 1959. That is why a foot to meter to foot round trip returns the original value apart from display rounding.
Use one direct conversion when you can. Pick the speed category, choose km/h as the source and m/s as the target so the tool converts through one base unit and avoids extra rounding.
The calculation uses 64-bit floating-point numbers, which give roughly 15 to 17 significant digits. The displayed answer trims trailing zeros, so very long decimals are intentionally shortened.
Related Tools
BMI Calculator
Calculate body mass index from height and weight. Shows WHO category, healthy-weight range and limitations of BMI.
Age Calculator
Calculate exact age in years, months and days from a birth date, plus total days, hours and the next birthday countdown.
One Rep Max Calculator
Estimate your one-rep max (1RM) from weight lifted and reps completed using Epley, Brzycki and Lander formulas.
Scientific Calculator
Evaluate supported real-number expressions with trig, logs, powers and parentheses locally in your browser.
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.
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.