Examples
| Task | Calculation | Answer |
|---|---|---|
| 20% of 150 | 150 × 20 ÷ 100 | 30 |
| 30 as % of 200 | 30 ÷ 200 × 100 | 15% |
| Change from 100 to 120 | (120 − 100) ÷ 100 × 100 | +20% |
| Add 10% to 200 | 200 × (1 + 10 ÷ 100) | 220 |
| Subtract 15% from 800 | 800 × (1 − 15 ÷ 100) | 680 |
How it's calculated
Percent of a number: multiply the number by the percent and divide by 100 — number × percent ÷ 100.
What percent one number is of another: divide the part by the whole and multiply by 100 — part ÷ whole × 100.
Percent change: subtract the old value from the new one, divide by the old value, and multiply by 100 — (new − old) ÷ old × 100. A positive result is an increase, a negative one is a decrease.
Add or subtract a percentage: multiply the number by (1 plus or minus the percent divided by 100) — number × (1 ± percent ÷ 100).
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 20% of 150 = 150 × 20 ÷ 100 = 30.
How do I find the percent change between two values?
Subtract the old value from the new one, divide by the old value, and multiply by 100. A positive result is an increase, a negative one is a decrease.
Why doesn't a number return to its original value after adding 20% and then subtracting 20%?
Because each percentage is calculated from a different base. 100 plus 20% is 120. But 20% of 120 is 24, not 20 — so 120 minus 20% gives 96, not 100.
How accurate is the calculation, and can I enter decimal percentages?
Yes, the calculator accepts decimal values (e.g. 8.5%) and shows the result with up to four decimal places.
Is any data sent to a server?
No, everything is calculated in your browser — nothing is sent anywhere.