Percent Error Calculator
Percent error and percent difference, which are not the same.
Work out Percent Error. Percent error and percent difference, which are not the same. Names the sign error before you make it.
The reference figure you are checking against. Cannot be zero — there is nothing to take a percentage of.
Percent error
5.000%
Your measurement read low
Percent error and percent difference are not the same calculation and get confused constantly. Percent error compares a measurement to a value you trust, and divides by that trusted value. Percent difference compares two measurements where neither is authoritative, and divides by their mean. Use percent error for a lab result against a literature value; use percent difference when comparing two runs of the same experiment. Percent error is conventionally reported unsigned, but the direction is worth knowing — a consistent bias in one direction points at a calibration problem rather than random scatter.
How the Percent Error Calculator works
Enter your measured value and the accepted one to get percent error, the absolute error and the direction of the bias. It also shows percent difference, because the two are constantly confused and they divide by different things.
Also known as: percentage error calculator · experimental error calculator · percent difference calculator · how to calculate percent error
Frequently asked questions
How do I calculate percent error?
Take the difference between your measurement and the accepted value, divide by the accepted value, and multiply by 100. Measuring 9.5 where the true value is 10 gives 5% error.
What is the difference between percent error and percent difference?
Percent error divides by a value you trust. Percent difference divides by the mean of two values where neither is authoritative. Use error for a result against a literature value, difference for two runs of the same experiment.
Should percent error be negative?
It is conventionally reported unsigned, since it measures how far off you were rather than which way. The direction still matters though — a bias consistently one way points at a calibration problem rather than random scatter.
What counts as a good percent error?
It depends entirely on the method. Analytical balance work should be well under 1%, a titration under 2%, and a rough volumetric estimate might reasonably be 5%. There is no universal threshold.
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