Percentage Calculator
Work out percentages, increases, decreases and what percent one number is of another.
Free Online Percentage Calculator
Percentages express a share of one hundred, which makes them the common language of discounts, tax rates, interest, exam marks, tips and statistics. The arithmetic is simple but easy to fumble under pressure — especially the difference between a percentage of a value and a percentage change between two values.
This calculator answers the three questions people actually ask, side by side: what is X% of Y, X is what percent of Y, and what is the percentage change from X to Y. All three update as you type, so you can sanity-check a number in a couple of seconds.
Key features
- Three calculators at once — percent of a value, one value as a percent of another, and percentage change.
- Signed change — increases show green with a plus, decreases show red, so the direction is never ambiguous.
- Division-by-zero guard — a zero base is flagged rather than silently returning a nonsense figure.
- Locale-aware output — results use your system number formatting for thousands and decimals.
This tool does its work inside your browser using native Web APIs. The files and text you give it are processed on your device and are not uploaded to our servers.
How to use: Percentage Calculator
- Pick the question you are asking
The three panels answer different questions. Reading the heading first avoids the classic mix-up between "20% of 80" and "20 is what percent of 80". - Enter your two numbers
Results appear immediately — there is no calculate button to press. - Read the result
Percentage change is signed: a positive figure is a rise, a negative figure is a fall relative to the starting value. - Sense-check the direction
A rise from 100 to 150 is +50%, but the fall from 150 back to 100 is only −33.3%. The base changes, so the two are not mirror images.
Technical specifications
| Processing location | Entirely in your browser — no server round trip |
|---|---|
| Data uploaded | None. Files and text never leave your device |
| Price | Free — no account, no trial, no usage cap |
| Category | Calculators |
| Works offline | Yes, once the page has loaded |
| Browser support | Chrome 90+, Edge 90+, Firefox 90+, Safari 15+ |
| Interface languages | English, 中文, हिन्दी, Español, العربية |
Frequently asked questions
How do I calculate a percentage increase?
Subtract the old value from the new one, divide by the old value, then multiply by 100. Going from 120 to 150 is (150−120)/120 × 100 = 25% increase. The original value is always the denominator.
Why is a 50% rise not cancelled by a 50% fall?
Because each percentage applies to a different base. 100 raised by 50% is 150; 150 reduced by 50% is 75, not 100. To reverse a 50% increase you need a 33.3% decrease.
How do I work out the original price before a discount?
Divide the sale price by (1 − discount/100). A £60 item after 25% off was £60 ÷ 0.75 = £80 originally. Do not add 25% back to the sale price — that gives the wrong answer.
What is the difference between percent and percentage points?
If a rate moves from 4% to 6%, that is a rise of 2 percentage points but a 50% increase. News reports often confuse the two, which can make a change sound far larger or smaller than it is.