Percent Error & Precision Calculator

Compare experimental observations with theoretical true reference values, or measure percent difference between two laboratory trials.

Lab Presets:

Percent Error Calculation

Observed / Experimental Value (V_obs)

Theoretical / Accepted True Value (V_true)

Measurement Analysis

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High Accuracy (< 5%)

📝 Step-by-Step Mathematical Derivation:

Percent Error: (|V_obs − V_true| / V_true) × 100

Percent Difference: (|V₁ − V₂| / Average) × 100

Absolute Error: |V_obs − V_true|

Relative Error: Absolute Error / |V_true|

What is percent error?

Percent error measures the accuracy of an experimental measurement against an accepted, established standard true value. By computing the ratio of absolute discrepancy relative to the true quantity and multiplying by 100, scientists eliminate scale differences to benchmark precision across disparate scientific fields.

Percent Error vs Percent Difference

Use Percent Error when you have a definitive theoretical reference standard (e.g. gravitational constant, published boiling point). Use Percent Difference when comparing two experimental trials where neither measurement can claim definitive authority.

Frequently asked questions

What is the percent error formula?▶

Percent error = (|Observed - True| / True) × 100. The absolute value keeps the result positive.

What is the difference between percent error and percent difference?▶

Percent error compares an experimental measurement to an accepted standard true value. Percent difference compares two experimental measurements against their average.

What is considered an acceptable percent error?▶

In general science and school laboratories, errors under 5% are considered excellent/acceptable. In industrial manufacturing, thresholds are typically below 0.1% to 1%.

Percent Error Calculator