Percentage Calculator
Calculate percentages instantly. Find a percentage of a number, calculate what percent one number is of another, measure percentage change, or work backward from a percentage.
Result
Every calculation runs in your browser — nothing is uploaded or stored on our servers.
About this percentage calculator
This calculator handles the four percentage questions people run into most often: finding a percentage of a number, working out what percent one number is of another, measuring the percentage change between two values, and increasing or decreasing a value by a percentage. Pick a mode, type two numbers, and you get the answer plus the calculation behind it. Everything runs in your browser — no sign-up, no data sent anywhere.
How to calculate a percentage of a number
To find X% of Y, divide the percentage by 100 and multiply by the number: (X ÷ 100) × Y. For example, 20% of 150 is (20 ÷ 100) × 150 = 30. This is the maths behind a "20% off" discount: a $150 item drops by $30 to $120. Percentages above 100 work the same way — 150% of 40 is 60.
How to find what percentage one number is of another
Divide the part by the whole and multiply by 100: (X ÷ Y) × 100. If you scored 30 out of 150 on a quiz, that's (30 ÷ 150) × 100 = 20%. The same formula tells you that $45 of a $180 bill is 25%, or that 12 of 48 sign-ups converted, which is 25%.
How to calculate percentage increase
Subtract the original value from the new value, divide by the original, and multiply by 100: ((new − original) ÷ original) × 100. Revenue that rose from $8,000 to $10,000 is a ((10,000 − 8,000) ÷ 8,000) × 100 = 25% increase. To grow a value by a set percentage instead, multiply by (1 + percent ÷ 100): 200 increased by 15% is 200 × 1.15 = 230.
How to calculate percentage decrease
The formula is the same as for an increase; the result is simply negative when the new value is lower. A price cut from $100 to $75 is a ((75 − 100) ÷ 100) × 100 = −25%, i.e. a 25% decrease. To reduce a value by a set percentage, multiply by (1 − percent ÷ 100): 200 decreased by 15% is 200 × 0.85 = 170.
How to calculate percentage change
Percentage change is the umbrella term for both increases and decreases: ((new − original) ÷ |original|) × 100. A positive result is an increase, a negative result is a decrease, and zero means no change. Percentage change from an original value of zero is undefined, because any amount is infinitely larger than nothing — in that case, use "what percent one number is of another" instead.
Common percentage formulas
- Percentage of a number: (X ÷ 100) × Y
- What percent X is of Y: (X ÷ Y) × 100
- Percentage change: ((new − original) ÷ |original|) × 100
- Increase by a percentage: value × (1 + percent ÷ 100)
- Decrease by a percentage: value × (1 − percent ÷ 100)
Practical examples
Percentages show up everywhere: a 15% tip on a $60 meal is $9; a shirt marked 30% off $50 costs $35; a student who got 42 of 50 questions right scored 84%; a subscriber base that grew from 1,200 to 1,500 is up 25%; and a warehouse holding 340 of 400 pallets is 85% full. All of these are one of the four modes above.
Quick examples
- 10% of 200 = 20
- 25% of 80 = 20
- 50% of 120 = 60
- 15% increase on 200 = 230
- 20% decrease on 100 = 80
Frequently asked questions
What is a percentage?
A percentage is a fraction expressed out of 100. "Percent" literally means "per hundred", so 25% is the same as 25/100, or 0.25. It's a convenient way to compare parts of different-sized wholes on a common scale.
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number: (X ÷ 100) × Y. For 20% of 150, that's (20 ÷ 100) × 150 = 30. Use the "Percentage of a number" mode above.
How do I find what percent one number is of another?
Divide the first number by the second and multiply by 100: (X ÷ Y) × 100. So 30 is (30 ÷ 150) × 100 = 20% of 150. Use the "What percent" mode.
How do I calculate percentage increase?
Take the difference between the new and original values, divide by the original, and multiply by 100. From 100 to 125 is ((125 − 100) ÷ 100) × 100 = a 25% increase.
How do I calculate percentage decrease?
Use the same formula as for an increase — the result is negative when the value drops. From 100 to 75 is ((75 − 100) ÷ 100) × 100 = −25%, a 25% decrease.
How do I calculate percentage change?
Percentage change covers both directions: ((new − original) ÷ |original|) × 100. Positive is an increase, negative is a decrease, zero is no change. It isn't defined when the original value is zero.
Can percentages be greater than 100%?
Yes. 100% is the whole amount, so anything larger than the whole is over 100%. Doubling a value is a 100% increase; tripling it is a 200% increase. This calculator accepts percentages of any size.
Can I use decimal numbers?
Yes. Every input accepts decimals and negative numbers where they make sense. Results are shown with sensible precision and without unnecessary trailing zeros.
Is this percentage calculator free?
Yes — completely free, with no account and no usage limits. It runs entirely in your browser.