Percent Error Calculator

Calculate the percent error between your measured result and the true or theoretical value.

Percent Error Calculator

Formula: % Error = |Experimental − Theoretical| / |Theoretical| × 100

Percent Error

1.631%

Excellent accuracy

Absolute Error

0.16

Underestimate

-0.16

Percent Difference (neither is true value)

1.6444%

Percent Error Calculator Formula & How It Works

% Error = |Experimental − Theoretical| / |Theoretical| × 100%
  • Experimental value: your measured or observed result
  • Theoretical (accepted) value: the known correct value
  • Absolute value ensures positive result
  • Lower % error = more accurate measurement

Percent error quantifies the accuracy of a measurement relative to a known standard. Example: you measure 9.6 g/cm³ for aluminum (theoretical: 2.70 g/cm³ — wait, theoretical = 2.70). % Error = |9.6 − 2.70| / 2.70 × 100 = 255.6% — indicating a large error. In science, < 5% error is often considered good. Different from percent difference (used when neither value is the 'true' one).

Percent Error Calculator FAQs

What is the difference between percent error and percent difference?

Percent error: compares experimental to a known theoretical value. Percent difference: compares two measured values with no 'correct' answer — uses average as denominator: |A−B|/((A+B)/2) × 100%.

What is an acceptable percent error in science?

Depends on the experiment and instrument precision. Physical measurements: < 5% is good. Chemistry experiments: < 3%. Analytical chemistry: < 0.5%. The acceptable error depends on the precision required and sources of experimental uncertainty.

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