Percent error calculator
Common in physics and chemistry labs and when checking estimates against reality. Enter the measured and true values.
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How to use it
- Enter measured value and true value.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Percent error = (|measured - true| ÷ |true|) × 100
Example
Inputs: Measured value = 9.8, True value = 10. Result: Percent error: 2%; Absolute error: 0.2.
Limits and caveats
- It gives the size of the error without its sign. Compare the two values directly to see whether the measurement was high or low.
Questions about this tool
I measured 9.8 and the reference is 10. What is the percent error?
The absolute error is 0.2. Divide by 10 and multiply by 100 to get 2%.
Can percent error be negative?
Not with this formula, since it uses absolute values. If your teacher wants the sign, use (measured - true) ÷ true × 100.
What percent error is acceptable in a lab?
It depends on the experiment and your instructor; there is no single threshold for every lab.