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Foundations of Physics

Percentage Uncertainty

The absolute uncertainty of a measurement divided by the measured value, expressed as a percentage.

Governing formula Percentage Uncertainty = (Δx / x) × 100%
SI unit %

In depth

Percentage uncertainty quantifies relative precision independent of measurement scale, allowing easy comparison of precision between small and large quantities.

Examples in the real world

For a mass measurement of 50.0 ± 0.5 g, the percentage uncertainty is (0.5 / 50.0) × 100% = 1.0%.