Calculate percent error, how far a measured or experimental value deviates from a known accepted value, expressed as a percentage.
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Percent Error = |Measured Value − Accepted Value| ÷ |Accepted Value| × 100. It's specifically used to express how far an experimental or measured result deviates from a known, accepted (true) value, always dividing by the accepted value, not the measured one. For example, measuring gravitational acceleration as 9.8 m/s² against the accepted 9.81 m/s² gives a percent error of about 0.10%.
Percent error assumes one of the two values (the accepted value) is authoritative, a known standard your measurement is being checked against. Our Percentage Difference Calculator instead compares two values symmetrically, with neither treated as more correct than the other, appropriate when you're simply comparing two measurements or estimates as peers.
This calculator uses the absolute value of the difference, so percent error is reported as a magnitude of deviation, regardless of whether the measured value was above or below the accepted value. The 'absolute error' figure shown alongside it is the raw (also absolute) numeric difference before converting to a percentage.
It depends entirely on the field and the precision of the measuring method, a percent error considered excellent in one context (say, a rough physical experiment) might be unacceptable in another (like precision manufacturing). There's no universal threshold.
If you're just comparing two values without either being an authoritative standard, use our Percentage Difference Calculator instead, which doesn't require designating one value as more correct than the other.
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