Percentage Calculator
Run any percentage calculation in one place. Eight modes cover everything you'll actually need: X% of Y, X is what % of Y, percentage change, X + Y%, X − Y%, percentage difference, percent error, and fraction → percent. Each mode has its own labels so you can't mix up which input means what — answer appears live as you type.
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.
When should I use percentage points instead of percent?
Use percentage points (pp) when comparing two percentages. If a rate moves from 5% to 7%, that's an increase of 2 percentage points — but a 40% increase in relative terms. News headlines often blur the two ('interest rates rose 2%' could mean either), which is misleading. In writing, say 'pp' or 'points' for absolute changes; reserve '%' for relative ones.