Percent Error Calculator
Calculate percent error between experimental and theoretical values.
Result
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A percent error calculator measures the accuracy of an experimental value by comparing it to a known theoretical value.
Examples
Chemistry lab
Measured boiling point 99.1°C vs theoretical 100°C: Error = |99.1-100|/100 × 100 = 0.9%
Physics experiment
Measured gravity 9.7 m/s² vs 9.8 m/s²: Error = |9.7-9.8|/9.8 × 100 = 1.02%
Large error
Measured 15 vs theoretical 10: Error = 5/10 × 100 = 50%
Frequently Asked Questions
What is percent error?
Percent error measures how far an experimental value is from the accepted (theoretical) value, expressed as a percentage of the theoretical value.
Can percent error be negative?
By convention, percent error uses absolute value and is always non-negative. Some fields use signed error to indicate direction.
What is a good percent error?
It depends on the field. In chemistry labs, under 5% is typically acceptable. In precision engineering, much lower errors are expected.
Result
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Quick Tips
- •Double-check your inputs — small errors lead to incorrect results.
- •Use decimal form for fractions when entering values.
- •Compare your percent error to accepted thresholds for your field to judge result quality.