％ Percentage Calculator
Find X% of a number, what percent one number is of another, percentage change, and percentage increase or decrease – with step-by-step working.
Quick answer: To find X% of Y, multiply Y by X ÷ 100 – for example, 15% of 200 = 30. To find what percent A is of B, divide A by B and multiply by 100.
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Percentage Calculator inputs
Result
What is 15% of 200?
15% of 200 = 30
Step by step
- Convert the percent to a decimal: 15 ÷ 100 = 0.15
- Multiply: 0.15 × 200 = 30
Quick examples:20% of 150 ·45 of 60 ·80 → 100 ·250 − 30%
Percentage formulas
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | X ÷ 100 × Y | 15% of 200 = 30 |
| X is what % of Y? | X ÷ Y × 100 | 30 of 200 = 15% |
| % change from X to Y | (Y − X) ÷ |X| × 100 | 80 → 100 = +25% |
| Increase X by Y% | X × (1 + Y ÷ 100) | 200 + 15% = 230 |
| Decrease X by Y% | X × (1 − Y ÷ 100) | 200 − 15% = 170 |
Everyday uses
Percentages appear everywhere: shop discounts, tips, sales tax, exam scores, salary raises, investment returns and statistics. A useful mental shortcut: 10% of any number is that number with the decimal point moved one place left, so 10% of 245 is 24.5 – double it for 20%, halve it for 5%.
Beware of reversing percentages: a 50% fall followed by a 50% rise does not return you to the start. 100 → 50 → 75. To undo a 50% drop you need a 100% increase.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For example, 15% of 200 = 0.15 × 200 = 30.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 30 out of 200 = 30 ÷ 200 × 100 = 15%.
How do I calculate percentage change?
Subtract the old value from the new value, divide by the old value and multiply by 100. Going from 80 to 100 is (100 − 80) ÷ 80 × 100 = 25% increase.
What is the difference between percent and percentage points?
If a rate rises from 10% to 12%, it increased by 2 percentage points but by 20 percent (because 2 is 20% of 10).