Percentage Calculator
Find a percent of a number, a ratio as a percent, or the change between two values.
Learn how it works: How to Calculate a Percentage IncreaseEnter both numbers to see your answer.
How to use the percentage calculator
Three tabs sit at the top, one for each kind of percentage question. Pick the tab that matches what you are after, then type your two numbers. The answer appears as you go.
- % of a number answers "what is 15% of 200?" The result is 30.
- X is what % answers "30 is what percent of 200?" The result is 15%.
- % change answers "200 grew to 250, by how much?" The result is a 25% increase.
How to calculate percentages by hand
Every percentage question reduces to one of three short formulas. Once you see the pattern, you can do most of them in your head.
To find a percent of a number, divide the percent by 100 and multiply: 15 ÷ 100 = 0.15, then 0.15 × 200 = 30. To find what percent one number is of another, divide and multiply by 100: 30 ÷ 200 = 0.15, then × 100 = 15%. For percent change, subtract the old value from the new, divide by the old, and multiply by 100: (250 − 200) ÷ 200 × 100 = 25%.
Common percentage examples
Percentages show up everywhere once you start looking. A few cases you will likely meet this week:
- A jacket marked 30% off a $80 price saves you $24, leaving $56.
- A 20% tip on a $45 dinner adds $9, for a $54 total.
- Sales tax of 8% on a $50 cart adds $4 at checkout.
- Scoring 42 out of 50 on a test works out to 84%.
Each one is just a tab on this calculator. Discounts and tips use "% of a number," test scores use "X is what %," and a price jump uses "% change."
Frequently asked questions
- How do I calculate a percentage of a number?
- Divide the percentage by 100, then multiply by the number. For 15% of 200: 15 divided by 100 is 0.15, and 0.15 times 200 is 30. The first tab does this for you.
- How do I find what percent one number is of another?
- Divide the first number by the second, then multiply by 100. So 30 out of 200 is 30 divided by 200, which is 0.15, times 100 equals 15%. Use the second tab for this.
- How do I calculate a percentage increase or decrease?
- Subtract the old value from the new one, divide by the old value, and multiply by 100. A rise from 200 to 250 is a 25% increase. A negative result means a decrease.
- How do I work out a discount?
- A discount is a percent of the original price. For 30% off $80, find 30% of 80, which is $24, then subtract it to get $56. The first tab gives you the discount amount.
- What does a negative percent change mean?
- It means the value went down. If something falls from 250 to 200, the change is negative 20%. The calculator adds a plus or minus sign so the direction is clear.
- Why can the total not be zero?
- Two of the modes divide by the total or starting value. Dividing by zero has no defined answer, so the calculator asks for a non-zero number instead of showing an error.