Percent Error Calculator
Use the Percent Error to work through percent Error from the values you enter. Review the notes below the result so you understand what the figure represents.
Percent error
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Absolute error —
Signed error —
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How it works
Percent error = |measured − true| ÷ |true| × 100How to use the Percent Error
Enter the requested values and start with one realistic example. Read the result together with its unit or label, then change one input at a time if you want to compare options.
Review the assumptions on the page and confirm any result that affects money, safety, technical work or another important decision.
Frequently Asked Questions
How do I calculate percent error?
Take the absolute difference between your measured and the accepted value, divide by the accepted value, multiply by 100. Measuring 9.6 m/s² against the true 9.81 gives (0.21/9.81)×100 ≈ 2.14%.
Can percent error be negative?
The standard convention uses absolute values, so no — though some fields keep the sign to show direction (over- vs under-estimate). This calculator shows both.
What is an acceptable percent error?
Context decides: under 5% is typical for school labs, under 1% for careful instrumentation, parts-per-million for metrology.