What is an acceptable percentage error?

Depends on the context. In most physics experiments, under 5% is acceptable. Precision experiments aim for under 1%.

What is the difference between error and uncertainty?

Error is the deviation from the true value. Uncertainty is the range within which the true value is believed to lie.

Percentage Error Calculator

Calculate the percentage error between an experimental and theoretical value.

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Use the formula and worked example below to calculate manually.

Overview

Percentage error quantifies the accuracy of an experimental measurement compared to the accepted theoretical (true) value. Use this in physics, chemistry, and engineering labs.

How to use this calculator

Enter the experimental (measured) value.
Enter the theoretical (accepted/true) value.
The calculator shows the percentage error and whether the measurement is above or below the true value.

Understanding the inputs & results

Experimental value

The value you measured or calculated in an experiment.

Theoretical value

The accepted, true, or expected value.

Absolute error

| Experimental − Theoretical |.

Percentage error

(|Experimental − Theoretical| / Theoretical) × 100.

The formula

Percentage error

% Error = |(Experimental − Theoretical)| / |Theoretical| × 100

The absolute difference between measured and true values, divided by the true value, expressed as a percentage. Lower is more accurate.

Worked example

Theoretical value of g = 9.8 m/s². Experimental measurement = 9.4 m/s².

|9.4 − 9.8| = 0.4.
% Error = (0.4 / 9.8) × 100 ≈ 4.08%.

✓ Percentage error ≈ 4.08% (below the true value).

Frequently asked questions

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