Percent Error Calculator

Find the percent error between a measured value and the true or accepted value.

Measured (experimental) value	9.6
True (accepted) value	9.81

Measured (experimental) value

True (accepted) value

Percent error

2.1407%

The measurement is off by 0.21, which is 2.1407% of the true value. It is below the true value.

Absolute error: 0.21
Signed error: -2.1407%

Measured vs true

Measured9.6
True9.81

1
Difference from the true value
|9.6 − 9.81| = 0.21
2
Divide by the true value, × 100
0.21 ÷ 9.81 × 100 = 2.1407%

About the Percent Error Calculator

Percent error shows how far an experimental result is from the accepted value, relative to that value. It's used in science lab reports. The absolute value means it's always positive; the signed error shows whether you were over or under.

The formula

% error = |measured − true| ÷ |true| × 100

Worked example

g measured as 9.6 m/s², accepted 9.81

|9.6 − 9.81| = 0.21
0.21 ÷ 9.81 × 100 = 2.14%

Questions people ask

What counts as a good percent error?

It depends on the experiment; under 5% is often acceptable in school labs.

Can percent error be negative?

The usual definition uses the absolute value, so it's always positive. The signed error shows whether you measured too high or too low.