Percentage Error Calculator
Compare an observed value with a reference value and calculate absolute error and relative percentage error.
Set your values
Adjust the values, then calculate your result.
How to use Percentage Error Calculator
- Enter the measurements or amounts in the fields above.
- Check that dimensions, rates and units match the labels.
- Select “Calculate percentage error” to see a clear estimate and the formula used.
How the percentage error calculator works
Absolute error = |observed − reference|. Relative percentage error = absolute error ÷ |reference| × 100 when the reference is nonzero.
Check your measurements and assumptions
Percentage error is undefined when the reference value is zero. Match units and sign conventions before comparing measurements.
Review the estimate before you act
Compare this result with an independent measurement, supplier quote or institution guidance when the decision matters. Confirm that the units and assumptions match the labels above, and update the inputs when the conditions change. Keep a note of the values used so you can reproduce the estimate later. This calculator is a planning aid and does not replace professional, product-specific or local guidance.
How do I calculate percentage error?
Subtract the reference from the observed value, take the absolute difference, divide by the absolute reference and multiply by 100.
Is input uploaded?
Processing takes place in your browser. This tool does not send your input or selected files to a conversion API.