How it works
Percent error = |measured − actual| ÷ |actual| × 100
The relative error keeps its sign, so a negative value means the measurement was too low. Percent error is used in science labs to judge how accurate an experiment was.
Percent error calculator
Enter the value you measured and the accepted (true) value. The calculator shows how far off the measurement is, as a percentage and as absolute and relative error.
Percent error
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Common questions
Can percent error be negative?
By the usual definition it uses the absolute value, so it is never negative. The signed relative error shows whether you were over or under.
What is a good percent error?
It depends on the experiment; in many school labs under 5% is considered good.