Percentage Calculator
Six percentage questions, each answered with the formula shown.
Start typing above and the result appears here.
Next step
How to use Percentage Calculator
Pick the question
Six shapes cover almost every percentage problem. Choosing the right one is most of the work.
Enter A and B
The labels above the answer tell you which number the calculator read as which.
Copy the working, not just the answer
The substituted formula is shown so you can paste it into an email or a homework answer.
Why use this percentage calculator
Runs on your device
Your input is handled entirely in this browser tab. Nothing is uploaded, so there is nothing for us to store, log or leak.
No sign-up, no quota
No account, no daily limit, no watermark and no email wall. Use it once or two hundred times a day.
Built to be linked
Options are stored in the URL, so a configured tool is a link you can send to a colleague or bookmark.
Technical notes
Every answer comes with the substituted formula, not just a number. That is the difference between a calculator and an answer you can defend in a meeting or a marked assignment. Percentage change additionally reports percentage points alongside percent, because conflating the two is the most common quantitative error in business reporting.
The six questions, with a worked example each
| Question | Example | Answer |
|---|---|---|
| What is A% of B? | 15% of 200 | 30 |
| A is what percent of B? | 30 of 200 | 15% |
| Percentage change A → B | 80 → 100 | 25% increase |
| Increase A by B% | 80 by 25% | 100 |
| Decrease A by B% | 100 by 20% | 80 |
| A is B% of what? | 80 is 80% of ? | 100 |
Supported
- Six question shapes covering standard percentage arithmetic
- The substituted formula for every result
- Percentage points reported alongside percent on change calculations
- Negative and decimal inputs
Limits and trade-offs
- Percentage change from zero is undefined and is reported as an error rather than as infinity.
- Results are rounded to four decimal places for display; the underlying arithmetic is full double precision.
- This is not compound interest. Repeated percentage changes need the compound interest calculator.
Last verified August 2026 · benchmarks re-run each quarter.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. 15% of 200 is 15 ÷ 100 × 200 = 30. Select "What is A% of B?" and the calculator shows that substitution with your own figures.
What is the difference between percentage change and percentage points?
If a rate moves from 5% to 6%, that is a rise of one percentage point and a rise of twenty percent. Both are correct and they mean very different things. This calculator reports both whenever you compute a change, because conflating them is the single most common percentage error in reporting.
How do I calculate percentage increase?
Subtract the old value from the new one, divide by the old value, and multiply by 100. From 80 to 100 is (100 − 80) ÷ 80 × 100 = 25%. The order matters: dividing by the new value instead gives 20%, which is a different question.
Why is a 50% rise followed by a 50% fall not back where it started?
Because each percentage applies to a different base. 100 rises by 50% to 150, then falls by 50% of 150, which is 75, landing at 75. Reversing a 50% increase requires a 33.3% decrease. Percentages do not commute.
How do I find the original price before a discount?
Use "A is B% of what number?". If an item costs 80 after a 20% discount, it is 80% of the original, so 80 ÷ 80 × 100 = 100. Do not add 20% to 80 — that gives 96, which is a common and expensive mistake.