Percentage Calculator
Four common percentage questions, one page: what a percentage of a number is, what percent one number is of another, and how much something changed.
What is X% of Y?
X is what % of Y?
Percentage change
The three formulas behind this tool
Percentage problems almost always reduce to one of three shapes. "What is X% of Y" multiplies Y by X divided by 100. "X is what percent of Y" divides X by Y and multiplies by 100. Percentage change subtracts the old value from the new one, divides by the old value, and multiplies by 100 — a negative result means a decrease.
Where this comes up
- Working out a discount or a tip on a bill
- Checking how much a salary, rent, or bill has gone up year over year
- Grading a test score as a percentage
- Comparing two time periods of sales or traffic data
Frequently asked questions
How do I calculate a percentage of a number by hand?
Multiply the number by the percentage, then divide by 100 — for example, 15% of 200 is 200 × 15 ÷ 100 = 30. The first calculator on this page does exactly that.
How do I work out what percentage one number is of another?
Divide the first number by the second, then multiply by 100 — for example, 30 out of 200 is (30 ÷ 200) × 100 = 15%. Use the second calculator above for this.
What's the difference between percentage change and percentage points?
Percentage change is a relative measure (going from 10% to 15% is a 50% increase), while percentage points measure the raw difference (a 5 percentage point increase). This tool calculates percentage change, not percentage points.
Why is my percentage change showing a negative number?
A negative result means the value decreased — for example, going from 200 to 150 is a −25% change. The calculator also labels it clearly as an increase or decrease alongside the number.