Percentage Calculator
Pick from 8 calculation modes — including % of a number, percentage change, percent error, percent difference and fraction-to-percent.
All calculations are done in your browser. Nothing is sent to a server.
How to use this percentage calculator
- Choose the calculation type from 8 tabs.
- Enter both numbers — labels update per mode.
- The result shows instantly with full label.
- Copy the result with one click.
Frequently asked questions
What is the difference between % change and % difference?
% change is directional ((new − old) / old). % difference is absolute and uses the average ((|A−B|) / ((A+B)/2)) — useful when neither value is the 'reference'.
What is percent error?
Percent error compares an actual measurement to an expected value: |actual − expected| / |expected| × 100. Used in science and engineering.
How do I convert a fraction to a percentage?
Divide the numerator by the denominator and multiply by 100. The fraction → % mode does this automatically.
Why doesn't 100 + 50% − 50% give me back 100?
Because each step is applied to the previous value, not the original. 100 + 50% = 150, then 150 − 50% = 75. Percentages don't cancel like opposite signs do. To find the rate that exactly reverses a change, use the % change mode with the new and original values.