Percent Error Examples for Labs and Measurement
On this page
Direct answer
Strong percent-error reporting names the measured value, reference value, units, signed error, absolute error, percent error and any relevant uncertainty or tolerance.
Formula and method
|measured−reference|/|reference| × 100
The calculation keeps full precision through the formula and rounds only the displayed answer.
Step-by-step calculation
- Identify a justified reference.
- Match units.
- Show signed and absolute error.
- Calculate the percentage and interpret it without overstating accuracy.
Worked examples
Mass
49.2 g vs 50.0 g: signed error −0.8 g; absolute error 0.8 g; percent error 1.6%.
Volume
24.7 mL vs 25.0 mL: 0.3 ÷ 25.0 × 100 = 1.2%.
Timing
3.08 s vs 3.00 s: signed +0.08 s; percent error 2.666…%.
Calibration
101.3 units vs 100.0: signed +1.3; percent error 1.3%.
Zero reference
0.04 vs 0: absolute error 0.04 units; percent error undefined.
Interpretation and edge cases
- A classroom accepted value may be a conventional reference, not unknowable exact truth.
- A single result cannot separate random error from systematic bias.
- Compare with a tolerance only when the method provides one.
Frequently asked questions
Does lower percent error always mean better measurement?
It indicates closer agreement with that reference for that observation, but does not fully describe uncertainty or repeatability.
Can I average percent errors?
Only with care; the aggregation method should match the measurement model.
What belongs in a lab report?
Values, units, method, result, rounding rule and uncertainty/tolerance context.
Sources and transparency
- JCGM VIM — Measurement error (2.16)
- JCGM VIM — Measurement result (2.9)
- JCGM VIM — Measurement accuracy (2.13)
The formulas and examples were evidence-checked on 2026-09-10. This is educational mathematical content. It does not replace a field-specific standard, accounting policy, laboratory method, contractual definition or professional judgment.
Keep exploring