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 runs entirely inside your browser using native Web APIs. Your files and text are never uploaded to a server, never logged and never shared with third parties.
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.