Percentage Calculator
Calculate X percent of a number, find what percent one value is of another, and measure the percent change between any two numbers instantly.
Percentage Calculator — A fast percentage calculator with three modes: find X% of a value, find what percent one number is of another, and measure the percent change between two numbers. Type your two values and the answer updates instantly. Every calculation runs entirely in your browser, so your numbers never leave your device.
What is Percentage Calculator?
The Percentage Calculator is a free online tool that handles the three percentage questions people ask most. Mode one finds X% of Y — for example a tip, a tax, or a discount amount. Mode two finds what percent X is of Y — useful for scores, completion rates, and shares of a total. Mode three measures the percent change from an old value X to a new value Y — handy for price increases, growth rates, and before/after comparisons. Pick a mode, type the two numbers, and the read-only result updates as you type. Results are formatted to your locale with up to six decimal places.
How to use Percentage Calculator
- Pick a mode with the segmented buttons: 'X% of Y', 'X is what % of Y', or '% change X → Y'.
- Type the first value into the top input (the percentage, the part, or the starting number depending on the mode).
- Type the second value into the second input (the base number, the whole, or the ending number).
- Read the answer in the read-only result field; it recalculates automatically whenever you change a value or switch modes.
- Switch modes at any time to reuse the same two numbers for a different question.
Examples
X% of Y: 20% of 150
Input
Mode: X% of Y, X = 20, Y = 150
Output
30
X is what % of Y: 45 of 180
Input
Mode: X is what % of Y, X = 45, Y = 180
Output
25
% change: from 80 to 100
Input
Mode: % change X → Y, X = 80, Y = 100
Output
25
Frequently asked questions
- What does each of the three modes calculate?
- 'X% of Y' returns Y × X ÷ 100 (e.g. 20% of 150 = 30). 'X is what % of Y' returns X ÷ Y × 100 (e.g. 45 of 180 = 25%). '% change X → Y' returns (Y − X) ÷ X × 100, so a rise from 80 to 100 is +25% and a drop from 100 to 80 is −20%.
- What happens if I enter zero or leave a field blank?
- If a field is empty or not a valid number, the result shows a dash (—). 'X is what % of Y' needs Y to be non-zero and '% change' needs the starting value to be non-zero, since dividing by zero is undefined; in those cases the result also stays a dash.
- Why is a decrease shown as a negative percent?
- Percent change keeps its sign: an increase is positive and a decrease is negative. Going from 100 to 80 is −20% because the value dropped by 20% of the starting number.
- How precise are the results?
- Results are shown with up to six decimal places and formatted for your locale, so thousands separators and the decimal mark match your region.
- Are my numbers sent to a server?
- No. Every calculation runs 100% client-side in your browser with no upload and no server communication, so the numbers you type never leave your device.
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