Percent Error Calculator

Compare a measured value against the accepted value.

Percent error
4.00%

Percent error uses the absolute difference, so it's always positive — it tells you how far off a measurement was, not which direction.

A worked example

Measuring 48 when the accepted value is 50 gives a percent error of 4%.

Frequently asked questions

Why use the absolute value of the difference?

Percent error measures how far off a measurement was, not which direction — taking the absolute value means an experimental result that's too high gives the same percent error as one too low by the same amount.

What counts as a 'good' percent error?

It depends entirely on the field and the measurement — some lab contexts expect well under 1%, while rougher estimates might consider 10-20% acceptable. There's no universal threshold.