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Math

Percent Error Calculator

Compare a measured value with a nonzero reference using absolute percentage error.

Exact method explained belowEditable inputs

Set up your calculation

Runs on your device

SOLUTION

Your result

Let’s calculate.

Use the Calculate button to see your result.

Review the method below for assumptions and conventions.

How to use this tool

  1. Enter measured value, reference value.
  2. Select Calculate to view the result.
  3. Check the method and assumptions below before using the result.

The method, explained

Percent error = |measured − reference| ÷ |reference| × 100. Signed error is also shown separately.

A WORKED EXAMPLE

A measurement of 98 against a reference of 100 has 2% error and signed error of −2.

What to keep in mind

The reference must not be zero. Percent error is not the same as relative change over time or percentage difference between two equally weighted values.

Common questions

Can the result be negative?

Absolute percent error is nonnegative. The signed error shows whether the measurement is above or below the reference.

What if the reference is very close to zero?

The percentage may be extremely large and unstable. Consider reporting absolute error as well.

Methodology maintained by ClarityKit. How these tools are built and checked.