About the percentage calculator
Answer the three percentage questions people ask most: what is X% of Y, what percent is one number of another, and how much did a value go up or down in percent. Results update as you type, and it runs in your browser.
How to use it
- Pick the card that matches your question.
- Type the two numbers into its boxes.
- Read the answer below the inputs; it updates as you type.
- Press Copy to grab the result.
Questions
- How do I calculate a percentage of a number?
- Divide the percentage by 100 and multiply by the number. For example, 20% of 150 is 0.20 × 150 = 30.
- How do I work out percentage increase or decrease?
- Subtract the old value from the new one, divide by the old value, and multiply by 100. Going from 50 to 75 is (75 − 50) ÷ 50 × 100 = a 50% increase.
- Why is the percent change from 0 undefined?
- Percent change divides by the starting value, and dividing by zero has no answer. Any move away from 0 would be an infinite percentage, so the calculator says so instead of printing Infinity.
- Is a 50% increase followed by a 50% decrease back to the start?
- No. 100 up 50% is 150, and 150 down 50% is 75. Each percentage applies to a different starting value.