Percentage Calculator
Three quick calculations that update as you type.
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result
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of the whole
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percentage change
Processed on your device — nothing is sent anywhere.
How it works
- Pick the row that matches your question: percent of a number, percent ratio, or percentage change.
- Type your numbers into the blanks. The result appears instantly as you type.
- Adjust either number to compare scenarios, or clear a field to start over.
Frequently asked questions
- How do I calculate a percentage of a number?
- Multiply the number by the percentage and divide by 100. For example, 15% of 80 is 80 × 15 ÷ 100 = 12. The first row of this calculator does exactly that and rounds the result to four decimal places.
- How do I work out what percent one number is of another?
- Divide the part by the whole and multiply by 100. If 30 students out of 120 passed, that is 30 ÷ 120 × 100 = 25%. The middle row of the calculator handles this pattern — enter the part first and the whole second.
- How is percentage change calculated?
- Subtract the starting value from the final value, divide by the starting value, then multiply by 100. Going from 50 to 65 is (65 − 50) ÷ 50 × 100 = 30%, an increase. A negative result means the value decreased.
- How do I calculate a percentage discount on a price?
- Multiply the original price by the discount percentage and divide by 100 to get the amount saved, then subtract it from the price. A 25% discount on $80 saves 80 × 25 ÷ 100 = $20, so you pay $60. Use the first row to find the discount amount, then subtract it yourself.
- What is the difference between percentage change and percentage points?
- Percentage points measure the simple difference between two percentages, while percentage change is relative to the starting value. Moving from 10% to 15% is a rise of 5 percentage points, but a 50% relative increase.
About this tool
This percentage calculator answers the three questions that cover almost every everyday percentage problem: what is X percent of a number, what percent is one value of another, and by what percent did a value change. Each question has its own row written as a fill-in-the-blank sentence, so you never have to remember which formula applies — just find the row that reads like your question and type in the two numbers.
All three calculations run locally in your browser with plain JavaScript. Results appear the moment you type, are rounded to four decimal places, and nothing you enter is sent to a server or stored anywhere. Because there is no network involved, the calculator responds instantly and keeps working offline once the page has loaded.
Common uses include shopping and tipping — finding 20% of a bill or the price after a discount — as well as schoolwork, where the percent-ratio row turns test scores like 42 out of 50 into a percentage. The percentage-change row is the one to reach for with prices, salaries, portfolio values or website statistics, since it correctly handles both increases and decreases and shows a negative sign when a value fell.
Two tips prevent the most common mistakes. For percentage change, always put the older value first: going from 50 to 65 is a 30% increase, but reversing the inputs gives a different answer because the change is measured relative to the starting point. And when comparing two percentages, remember the difference in percentage points is not the same as the relative change — the last FAQ entry explains the distinction with an example.