Experimental data & uncertainty · SL/HL

Percentage uncertainty

Express an absolute uncertainty as a percentage.

Your values

Number formats & units

Use decimal dots in datasets. Single values also accept decimal commas and scientific notation such as 1.2e-3 or 1.2 × 10⁻³.

Calculated locally. No account or input upload.

Example

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\text{percentage uncertainty}=\frac{\text{absolute uncertainty}}{|\text{measured value}|}\times100\%

What the variables mean

Symbol	Meaning
absolute uncertainty	The ± range associated with the measurement.

(25.0 ± 0.5) mm

Follow the example steps

percentage uncertainty = Δx/|x| × 100
= 0.5/|25| × 100 = 2%
Report the value to the same decimal place as the rounded absolute uncertainty: (25.0 ± 0.5) mm

Use matching units for the value and its absolute uncertainty.

x = 10 cm, Δx = 1 mm: 100 × 1/10 = 10%

Δx = 0.1 cm: 100 × 0.1/10 = 1%

More checks before you submit

Do not confuse SD/SE from repeated data with instrument resolution unless the context justifies it.

Method notes

State uncertainties to a sensible precision and keep the value to the same decimal place as its absolute uncertainty.