📏 Percentage Error Calculator

About this Percentage Error Calculator

Percentage error measures how far a measurement or experiment landed from the accepted true value, expressed as a percentage of that true value. It is the standard accuracy score in school and university labs: |experimental − theoretical| ÷ |theoretical| × 100. This calculator also shows the absolute error and the signed difference, so you can see the direction of the miss.

How to use it

1. Enter the value you measured or calculated (experimental).
2. Enter the accepted true value (theoretical).
3. Click Calculate % error.
4. Read the percentage error, absolute error and whether you measured high or low.

Example

Measuring gravity as 9.8 against a true 9.81 gives an absolute error of 0.01 and a percentage error of about 0.102%.

Frequently asked questions

Can percentage error be negative?

The standard percentage error is always positive because it uses the absolute difference. The signed difference shown here can be negative and tells you the direction of the error.

What is a good percentage error?

In school labs under 5% is usually acceptable and under 1% is excellent — but it depends on the equipment and the experiment.

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