Percent Error Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
100% FreeRuns in your browserBasic
Enter Values
Enter your values and press Calculate to see results.
How to use this calculator
- Enter your measured value and the actual value.
- Read the percent error.
How it works
Percent error = |measured − actual| ÷ |actual| × 100 — how far off the measurement is, relative to the true value.
Worked example
Measured 98, actual 100. |98 − 100| ÷ 100 × 100 = 2% error.
Common mistakes
- Dividing by the measured value instead of the actual one.
- Reporting a negative — percent error uses the absolute difference.
Frequently asked questions
Is percent error always positive?
Yes — it uses the absolute difference, so it shows the size of the error regardless of direction.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.