Percent Calculator
A stripped-down percent answer box. Skip the formula hunt: pick one of the three slots - “what is ___% of ___”, “___ is what % of ___”, or “___ is ___% of what” - fill two of the three numbers, and the third appears. Every answer is accompanied by the exact equation used, so you can sanity-check the result or drop it into a document.
How to use the percent calculator
-
1
Pick a sentence
Choose the phrasing that matches your question: what is X% of Y, Y is what % of X, Y is X% of what.
-
2
Fill the two known boxes
Leave the answer box blank; fill the other two with your numbers.
-
3
See the result
The calculator solves for the missing number and shows the equation.
-
4
Copy or try another
Copy the answer or tweak the inputs to explore related questions.
Quick answers you probably want
| Question | Answer |
|---|---|
| 10% of 250 | 25 |
| 7.5% of 80 | 6.00 |
| 15% tip on 63.20 | 9.48 |
| 40 is what % of 160 | 25% |
| 120 is what % of 80 | 150% |
| 18 is 6% of what | 300 |
| Increase 500 by 12% | 560 |
| Decrease 500 by 12% | 440 |
Percent vs decimal
Percentages and decimals are the same number written differently:
- 50% = 0.5
- 12.5% = 0.125
- 200% = 2.0
- 0.4% = 0.004
Multiplying by a percent is multiplying by that decimal. If the calculator says 80 * 0.15 = 12, that is the same operation as “15% of 80 = 12”. Dropping into decimal form is often the fastest way to spot an error: 350% of 40 cannot be 14, because 3.5 times 40 is 140.
Watch out for
- Two-step deals that don’t stack. “20% off, then another 10% off” is a 28% discount, not 30%. Each percent is applied to the new price.
- Compound interest. 5% per year for 10 years is not 50% total - it is
(1.05)^10 - 1 = 62.9%. Use a compound interest tool, not this one. - Tax on top of tip. Check your local convention - some places tip on pre-tax, others on post-tax totals.
Frequently Asked Questions
The Percentage Calculator walks through every percent mode separately (of-a-number, what-percent, increase, decrease). This one is a single compact “fill in the blanks” view for the three classic percent questions. Pick whichever UI you prefer.
Yes. A negative value represents a reduction. “Increase 200 by -15%” gives 170, same as “decrease 200 by 15%”.
Use decimals (0.5, 3.75). The calculator does not parse fractions like 1/4 - convert to 0.25 first or use the fraction-to-percent tool if you have one.
No. All math happens in the browser and nothing you type leaves your device.
Related Tools
Age Calculator
Calculate exact age in years, months and days from a birth date, plus total days, hours and the next birthday countdown.
BMI Calculator
Calculate body mass index from height and weight. Shows WHO category, healthy-weight range and limitations of BMI.
BMR Calculator
Estimate your basal metabolic rate — the calories you burn at complete rest. Uses the Mifflin-St Jeor equation, the current clinical standard.
Calorie Calculator
Estimate daily calorie needs for your goal using Mifflin-St Jeor BMR and activity factors. Includes deficit and surplus targets.
CD Calculator
Calculate the interest and final balance on a Certificate of Deposit. Handles compounding frequency and early withdrawal penalties.
Concrete Calculator
Calculate how much concrete you need for slabs, footings, columns and walls. Get cubic yards, bag counts and material cost estimates.