Percent Error Calculator

Enter your measured (experimental) value and the accepted (theoretical) value.

Measured (experimental) valueActual (theoretical) value

Percent error

2.14%

|9.6 − 9.81| = 0.21

0.21 ÷ |9.81| × 100 = 2.14%

Percent error formula

Percent error = |Measured − Actual| ÷ |Actual| × 100

If you measured gravity as 9.6 m/s² and the accepted value is 9.81, the error is |9.6 − 9.81| = 0.21, and 0.21 ÷ 9.81 × 100 = 2.14%.

Lab reports usually want the absolute value. The signed error shows direction: negative means your measurement came in low.

Percent error compares to a known true value. When neither value is “correct”, use the percentage difference calculator.

Can percent error be negative?

Signed percent error can be. The standard formula uses absolute value, so the result is positive.

What is an acceptable percent error?

In many school labs under 5% is considered good, but the threshold depends on the experiment.

Why can't the actual value be zero?

The formula divides by the actual value, and division by zero is undefined.