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Percentage Calculator
Three everyday percentage questions in one place. Type in any box and the answers update instantly.
Percentage formulas
| Question | Formula | Example |
|---|---|---|
| What is P% of X? | X × P ÷ 100 | 15% of 80 = 12 |
| A is what % of B? | A ÷ B × 100 | 30 of 120 = 25% |
| % change from A to B | (B − A) ÷ A × 100 | 50 → 65 = +30% |
| Find the whole from a part | Part ÷ P × 100 | 12 is 15% of 80 |
Percentage points vs percent
If a rate rises from 4% to 5%, it went up by 1 percentage point, but by 25 percent (1 ÷ 4). News reports and loan offers mix these up all the time, so check which one is meant.
Quick mental math
- 10%: move the decimal point one place left. 10% of $85 is $8.50.
- 5%: half of 10%. 5% of $85 is $4.25.
- 20%: double 10%. 20% of $85 is $17.
- Percentages are reversible: 8% of 25 is the same as 25% of 8, which is 2.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. 15% of 80 is 80 × 15 ÷ 100 = 12.
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value and multiply by 100. From 50 to 65 is (65 − 50) ÷ 50 × 100 = 30% increase.
Is a 50% drop then a 50% rise back to even?
No. 100 falling 50% is 50, and a 50% rise on 50 is only 75. After a 50% fall you need a 100% rise to get back to where you started.