Percent Error Calculator

Enter a measured value and the true value. Get the absolute percent error and the signed error.

Measured value

True value

If your reference can be zero, percent error is not defined. Consider using absolute difference instead.

How it works

Percent error compares how far a measurement is from the true value. The absolute version ignores sign, while the signed version shows whether you measured high or low.

Absolute percent error = |Measured − True| ÷ |True| × 100
Signed percent error = (Measured − True) ÷ True × 100

Example. Measured 9.78 with a true value of 9.81. The difference is −0.03. Absolute percent error = |−0.03| ÷ 9.81 × 100 ≈ 0.31%. Signed percent error ≈ −0.31%.

When this helps

Lab measurements and experiments
Quality control and manufacturing checks
Calibration and instrument comparisons
Data validation in reports

Results are rounded to two decimals for percentages and four for absolute error. Adjust the rounding if you need more precision.

Explore more in the percentage tools hub.