Percentage Calculator
Find a percentage of a number, what percent one number is of another, or percentage change.
Calculate any of the three most common percentage problems — a percentage of a number, what percent one value is of another, or the percentage increase or decrease between two numbers — with instant results and the exact formula shown for each.
How to use Percentage Calculator
- 1Enter your input for percentage calculator.
- 2Review the result on this page.
- 3Download or copy your result.
The three percentage formulas explained
"X% of Y" answers questions like a discount amount: 20% of a $150 item is (20 ÷ 100) × 150 = $30 off, making the final price $120. "X is what % of Y" flips that around — if you scored 45 out of 60 on a test, that's (45 ÷ 60) × 100 = 75%. "Percentage change" measures growth or decline between two values: if a stock moved from $80 to $92, the change is ((92 − 80) ÷ 80) × 100 = +15%; if it dropped from $80 to $68, that's ((68 − 80) ÷ 80) × 100 = −15%.
The formulas look similar but answer genuinely different questions, which is why mixing them up is the most common percentage mistake — this calculator keeps the three modes clearly separated so you always know which calculation you're getting.
Everyday situations where you need percentages
Working out a discount or sale price, calculating a tip or service charge, figuring out what grade a test score represents, comparing salary raises or price increases year over year, and computing what portion of a budget a specific expense represents. Percentage change specifically is the calculation behind most "how much did this grow" questions — revenue growth, weight change, population change, or investment returns over a period.
Frequently Asked Questions
What percentage calculations does this tool support?
Three common ones: finding X% of a number, finding what percentage one number is of another, and calculating the percentage increase or decrease between two values.
How is percentage increase or decrease calculated?
(New Value − Old Value) ÷ Old Value × 100. A positive result is an increase; a negative result is a decrease.
Is this tool really free?
Yes, Percentage Calculator is completely free to use — no sign-up, no hidden charges.