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How It Works
Percent error tells you how far a measured value strays from a known or accepted value. It divides the absolute difference by the accepted value and multiplies by 100. A lower percent error means your measurement was more accurate.
Example Problem
A student measures the boiling point of water at 99.1°C. The accepted value is 100°C.
- Difference: |99.1 − 100| = 0.9
- Percent error: (0.9 / 100) × 100 = 0.9%
Frequently Asked Questions
What is the difference between percent error and percent difference?
Percent error compares a measurement to a known standard. Percent difference compares two equal-status measurements and divides by their average. Use percent error when one value is the accepted truth.
Is a percent error of 5% acceptable?
It depends on the field. In a chemistry lab, 5% is often acceptable for student experiments. In precision manufacturing or pharmaceutical work, tolerances of less than 1% are common.
Can percent error be over 100%?
Yes. If the measured value is more than double or less than zero compared to the accepted value, the percent error exceeds 100%. This usually indicates a major experimental problem.
Related Calculators
- Percent Difference Calculator — compare two measurements without a known standard.
- Percent Yield Calculator — evaluate chemical reaction efficiency.
- Statistics Calculator — compute mean and standard deviation for measurement analysis.
- Percent Off Calculator — apply percentage calculations to everyday discounts.
- Z Score Calculator — determine how far a value lies from the expected mean.