Percentage Calculator
The three percentage questions everyone asks — answered live as you type.
What is X% of Y?
X is what percent of Y?
Percentage change
About this tool
Discounts, tips, tax, grades, statistics — percentages are everywhere, and they come in three shapes: what is 15% of 80 (finding a part), 12 is what percent of 80 (finding the rate), and from 80 to 92 is what change (finding growth or decline). This calculator handles all three side by side, updating the instant you type, with no buttons to press.
The three formulas
- X% of Y = Y × X ÷ 100 — e.g. 15% of 80 = 12.
- X as a % of Y = X ÷ Y × 100 — e.g. 12 of 80 = 15%.
- Change from A to B = (B − A) ÷ A × 100 — e.g. 80 → 92 = +15%.
Frequently asked questions
How do I calculate X percent of a number?
Multiply the number by the percentage and divide by 100: 15% of 80 is 80 × 15 ÷ 100 = 12. The first calculator does this for you as you type.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100: 12 out of 80 is 12 ÷ 80 × 100 = 15%. Use the second calculator for this.
How is percentage change calculated?
Subtract the old value from the new value, divide by the old value, and multiply by 100. Going from 80 to 92 is (92 − 80) ÷ 80 × 100 = +15% — an increase; a negative result is a decrease.
What is the difference between percentage change and percentage points?
If a rate moves from 10% to 15%, it rose 5 percentage points, but the relative change is 50%. Percentage points compare two percentages directly; percentage change compares relative size.
Can I use decimals and negative numbers?
Yes — all three calculators accept decimals (like 2.5) and negative values, and round results sensibly to at most four decimal places.