Percent Error Calculator
Experimental accuracy against a true value.
Enter your values
Enter the measured value you are working with.
Enter the accepted (true) value you are working with.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Percent error
- 0.9174%
- Absolute error
- 0.09
- Relative error
- 0.009174
- Direction
- Underestimate
- Accuracy
- 99.0826%
Working
- 1% error = |9.72 − 9.81| ÷ |9.81| × 100 = 0.9174%
Quick answer
Percent error is the absolute difference between measured and true value, divided by the true value, times 100.
% error = |measured − true| ÷ |true| × 100
At a glance
| What it does | Experimental accuracy against a true value. |
|---|---|
| Category | Math |
| Inputs needed | Measured value, Accepted (true) value |
| Main output | Percent error |
| Formula | % error = |measured − true| ÷ |true| × 100 |
| Cost | Free — no sign-up, no download |
How to use the Percent Error Calculator
- 1Enter your measured or experimental value.
- 2Enter the accepted or theoretical value.
- 3Read the percent error and accuracy.
Inputs explained
- Measured value
- Enter the measured value you are working with.
- Accepted (true) value
- Enter the accepted (true) value you are working with.
Worked example
Using the values the calculator loads with:
Inputs
- Measured value9.72
- Accepted (true) value9.81
Results
- Percent error0.9174%
- Absolute error0.09
- Relative error0.009174
- DirectionUnderestimate
- Accuracy99.0826%
- % error = |9.72 − 9.81| ÷ |9.81| × 100 = 0.9174%
Frequently asked questions
What is an acceptable percent error?
In school labs under 5% is usually good; precision physics work targets far below 1%.
Can percent error be negative?
By convention it uses absolute value, but the direction row above tells you whether you were high or low.
What do I need to enter into the Percent Error Calculator?
Just 2 values: measured value, accepted (true) value. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Percent Error Calculator work out the answer?
Percent error is the absolute difference between measured and true value, divided by the true value, times 100. It applies the formula % error = |measured − true| ÷ |true| × 100 and shows the working so you can check each step by hand.
Is the Percent Error Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.