Percentage Calculator
Work out X% of a number, what percent one number is of another, and any percentage increase or decrease.
What is X% of Y?
X is what percent of Y?
Percentage change from X to Y
The formulas
- What is X% of Y?
- (X ÷ 100) × Y
- X is what percent of Y?
- (X ÷ Y) × 100
- Percentage change from X to Y
- (Y − X) ÷ X × 100
About the Percentage Calculator
This free percentage calculator answers the three percentage questions people actually ask: what is X% of a number, what percent one number is of another, and how much a value went up or down in percent. Type into any row and the answer appears instantly — no button to press, no formulas to remember.
It covers everyday maths in one place: working out a 15% discount or tip, checking what a test score is as a percentage, or measuring a price increase between two amounts. The side panel shows the exact formula behind each answer, so you can learn the calculation while you use it.
Everything runs entirely in your browser — the numbers you enter are never uploaded, and the page keeps working offline once loaded.
Frequently asked questions
Answers to the questions we hear most about this tool.
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number: (X ÷ 100) × Y. For example, 20% of 150 is (20 ÷ 100) × 150 = 30. The first row of this percentage calculator does exactly that — enter 20 and 150 and it shows 30 instantly.
How do I find what percent X is of Y?
Divide X by Y and multiply by 100: (X ÷ Y) × 100. For example, 45 of 60 is (45 ÷ 60) × 100 = 75%. It is the calculation behind test scores, market shares and progress — the second row of the calculator handles it.
How is percentage increase or decrease calculated?
Subtract the start value from the end value, divide by the start value, then multiply by 100: ((Y − X) ÷ X) × 100. Going from 80 to 100 is a 25% increase; going from 100 to 80 is a 20% decrease. Note the two are not symmetrical because the base value changes.
How do I work out a discount?
Use the first row: enter the discount percentage and the price. 25% of $80 is $20, so the discounted price is $80 − $20 = $60. Or use the change row backwards: from the old price to the sale price, it tells you the exact percent off.
Is this percentage calculator free and private?
Yes — completely free, with no sign-up and no limits. Every calculation runs locally in your browser with JavaScript; the numbers you type are never sent to a server, and the tool keeps working even offline once the page has loaded.
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