Percentage Calculator
Find a percentage of a number, what percent one number is of another, and percentage increase, decrease or difference.
How to use the Percentage Calculator
- Choose the kind of calculation from the drop-down, such as “What is X% of Y?” or “Percentage change from A to B”.
- Type the two values. Decimals, negative numbers and thousands separators (1,250.50) are accepted.
- Read the result, the formula and the step-by-step working that appear instantly.
- Use Copy result to paste the answer elsewhere, or Reset to start again.
Good to know
- Percentage change is calculated as (B − A) ÷ |A| × 100, using the absolute value of the starting value so the sign of the result always shows the direction of the move. It is undefined when A is 0.
- Percentage difference is symmetric: |A − B| ÷ ((A + B) ÷ 2) × 100, so swapping the values gives the same answer. It is undefined when both values are 0 or when they average to 0.
- “X is what percent of Y” needs Y to be non-zero; the calculator says so rather than showing Infinity or NaN.
- Results are cleaned of binary floating-point noise (so 0.1 + 0.2 shows 0.3) and shown to at most 10 decimal places with trailing zeros removed.
Examples
- A discount
- What is 15% of 200? Choose “What is X% of Y?”, enter 15 and 200. Result: 30.
- Price after a rise
- A price of 80 increased by 25% becomes 100 (an extra 20).
- Growth between two figures
- From 50 to 65 is a 30% increase. From 65 back to 50 is a 23.0769230769% decrease, because the base differs.
Frequently asked questions
What is the difference between percentage change and percentage difference?
Percentage change measures movement from an old value to a new one and depends on direction. Percentage difference compares two values with neither treated as the original, using their average as the base, so the order does not matter.
Why is a 50% increase followed by a 50% decrease not back to the start?
Each percentage applies to a different base. 100 up 50% is 150, and 50% of 150 is 75, so the second step removes more than the first added.
Can I use negative numbers?
Yes. A negative percentage reverses the direction (increasing by −20% is the same as decreasing by 20%), and a negative starting value is handled by the absolute-value rule for percentage change.
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