Percentage Error Calculator
Error % = |Observed − Actual| ÷ |Actual| × 100|110 − 100| ÷ 100 × 100 = 10%
Free online tool
Percentage Error Calculator
Measure how far an observed value is from the actual value, as a percentage.
Instant calculation
Calculate percentage error
Compare an observed measurement with the actual value.
Your result
Calculation
Your numbers stay in this browser. Nothing is uploaded or saved.
Three clear steps
How to use this calculator
- 01
Enter observed value
Type the value you measured or observed.
- 02
Enter actual value
Type the true or accepted value.
- 03
Calculate error
See the percentage error between the two values.
The formula
How this calculation works
Take the absolute difference between observed and actual, divide by the absolute actual value, multiply by 100.
Check the method
Worked examples
Each example follows the same formula used by the calculator.
Observed 110, actual 100 — error?
|110 − 100| ÷ 100 × 100 = 10%10% errorObserved 95, actual 100 — error?
|95 − 100| ÷ 100 × 100 = 5%5% errorCommon questions
Questions about this calculation
What is percentage error?
It measures the difference between an observed value and the actual value, expressed as a percentage. Formula: |observed − actual| ÷ |actual| × 100.
What if the actual value is zero?
The calculator shows an error. Percentage error is undefined when the actual value is zero because it would require division by zero.
When is percentage error used?
In science, engineering, manufacturing and quality control to measure accuracy of measurements, experiments or production outputs.
Can the percentage error be negative?
The formula uses absolute values, so percentage error is always positive. It represents magnitude of error, not direction.
How is percentage error different from percentage difference?
Percentage error compares observed to actual (a known reference value). Percentage difference treats both values equally with no reference.
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