Percentage calculator
Find a share, calculate an amount from a percent, or measure percentage change.
- 1Add input
- 2Adjust settings
- 3Get your result
Tool input and files are processed in this browser without being uploaded.
Before you start
Choose the question you need to answer. Each mode labels its two inputs and shows the formula, so you can see which value is the whole or starting point.
How to use this tool
- Choose whether to find a share, an amount from a percentage, or a percentage change.
- Enter the two values using the labels shown for that calculation and check the formula.
- Calculate, then read the result with its label and percent sign where applicable. Copy or download it if needed.
Supported inputs and limits
A whole or starting value of zero makes a percentage ratio undefined and is rejected. The “percentage of a value” mode can use zero.
Percent change compares two numbers; it cannot make periods, audience sizes, or measurement methods comparable. Normalize your data before interpreting the result.
Results are calculated in this browser; refresh clears unsaved work.
Worked example
Example input
Part: 25 Whole: 200
Example options
Calculation: X is what % of Y?
Example output
12.5%
When something does not work
If calculation fails, enter finite numbers and check the denominator or starting value for zero. Changing an input marks the previous result as outdated.
Frequently asked questions
Why does one result have no percent sign?
“What is X% of Y?” returns an amount, such as 20% of 100 = 20. The share and change modes return percentages.
Can I calculate a percentage change from zero?
No. Percentage change divides by the starting value; when that value is zero, the percentage is undefined. Use the absolute difference instead.
What if the starting value is negative?
The change mode uses (ending − starting) ÷ starting × 100. With a negative starting value, the sign can feel counterintuitive; check whether this signed-baseline formula fits your context.
Documentation & further reading
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