Percent Error Calculator

Enter your measured or experimental value and the accepted true value. Percent error shows how far off the measurement is, relative to the true value.

Percent error

Percent error2.1407%
Signed error
−2.1407% (measured is too low)
Absolute error
0.21
Relative error
0.0214067278

Working

  1. Error = measured − actual = 9.6 − 9.81 = −0.21
  2. Percent error = |−0.21| ÷ |9.81| × 100 = 2.1407%

Formula

percent error = |measured − actual| ÷ |actual| × 100%

measured
the value you obtained
actual
the accepted, theoretical or true value

Worked example

Measuring gravitational acceleration

  1. Measured: 9.6 m/s²; accepted: 9.81 m/s²
  2. Error: 9.6 − 9.81 = −0.21
  3. Percent error: 0.21 ÷ 9.81 × 100 = 2.14%

The measurement is 2.14% too low.

Percent error vs percentage difference vs percentage change

  • Percent error compares a measurement against a known correct value; the true value is the reference.
  • Percentage difference compares two values when neither is “correct”, using their average as the reference — see the percentage difference calculator.
  • Percentage change compares a new value with an old one — see the percentage increase calculator.

Signed or absolute?

Most science classes report percent error as a positive number (the absolute value). The signed version keeps the direction: negative means the measurement is too low, positive means too high. Both are shown so you can use whichever your course or lab expects.