Values
Enter numbers or use sliders. Scientific notation like 1.2e-3 is accepted.
Formulas
Percent error = |E − T| / |T| × 100% (T ≠ 0)
Absolute error = |E − T|
Relative error = |E − T| / |T| (same as percent error as a decimal)
Compare multiple experiments
One trial per line: Trial1, 9.5, 10 or 9.5 10 (uses default names).
| Name | E | T | |% error| |
|---|
Practice
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What is percent error?
Percent error tells you how far a measured value is from the accepted or theoretical value, as a percentage of that true value. It uses the absolute difference so the result is never negative.
Why it matters in experiments
It helps you judge instrument quality, procedure, and random error. Comparing percent error across trials shows consistency.
How to reduce error
- Calibrate equipment; use appropriate precision.
- Repeat measurements and average when possible.
- Control variables and follow consistent technique.
Embed
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FAQ
- What is the percent error formula?
- Percent error = |experimental − theoretical| ÷ |theoretical| × 100%, when the theoretical value is not zero.
- How do you calculate percent error?
- Subtract the true value from your measured value, take the absolute value, divide by the absolute true value, and multiply by 100.
- What is a good percent error?
- It depends on the experiment. Under about 1% is often excellent for instructional labs; 1–5% may be acceptable; larger values suggest reviewing procedure or equipment.
- What does percent error mean?
- It is the size of the mistake relative to the true value — not the absolute size alone — so comparing errors at different scales is fairer.