Percentage Error Calculator
Percentage error expresses how far an estimate or measurement is from the accepted true value, as a percentage. Essential for lab reports, forecasts and quality control.
Worked example
Estimated 105 vs actual 100: (5 ÷ 100) × 100 = 5%
How to calculate
- Enter the estimated or measured value.
- Enter the actual (true) value.
- Read the percentage error — lower means more accurate.
Formula
Error = (|Estimated − Actual| ÷ |Actual|) × 100
Explanation
- Physics and chemistry lab reports.
- Forecast accuracy in business planning.
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Use CalculatorFrequently Asked Questions
What is a good percentage error?
It depends on the field: school labs often accept under 5–10%, while engineering tolerances can be far stricter. Always compare against the accepted standard for your context.
Can percentage error be negative?
No — the formula uses the absolute difference, so the error is always positive. The direction of the mistake is reported separately in lab work.