Percent Error Calculator

Calculate the percent error between an observed (measured) value and a true (accepted) value. Useful for lab reports, measurement accuracy checks, and forecast-vs-actual comparisons.

Your Result

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ResultWhat it means?
< 1%ExcellentErrors below 1% indicate very high measurement accuracy.
1 – 5%GoodErrors between 1% and 5% are typical for many scientific measurements.
5 – 10%AcceptableErrors between 5% and 10% are reasonable for rough estimates and field measurements.
10 – 25%PoorErrors between 10% and 25% suggest a noticeable discrepancy worth investigating.
≥ 25%Very poorErrors of 25% or more indicate a significant mismatch between observed and true values.
—No resultInputs are out of range or the true value is zero.

Percent Error Formula

Percent Error=|observed − true||true|

Percent error is the absolute difference between observed and true values, divided by the absolute true value, expressed as a percentage.

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