Calibration · Glossary

What is Measurement Uncertainty?

doubt about a resultCalibration

Measurement uncertainty is a quantified range around a result within which the true value is expected to lie with a stated confidence.

Measurement Uncertainty Explained

Every measurement has some doubt. The GUM method lists each source, converts it to a standard uncertainty, combines them as root sum of squares and expands the result with a coverage factor.

A calibration result without its uncertainty cannot be used to make a pass or fail decision with confidence.

Measurement Uncertainty Formula

u_c = √(Σ u_i²) and U = k × u_c

u_i	standard uncertainty of each source
k	coverage factor, 2 for about 95 %

Example: Sources 0.010, 0.020 and 0.005 bar: u_c ≈ 0.023 bar, U ≈ 0.046 bar (k = 2).

Calculators for Measurement Uncertainty

CalculatorMeasurement Uncertainty CalculatorFree online calculator with formula and worked example.CalculatorCoverage Factor CalculatorFree online calculator with formula and worked example.

Free Downloads

Free downloadMeasurement Uncertainty Budget Excel SheetFree download in Excel and PDF.Free downloadCalibration Certificate Format in ExcelFree download in Excel and PDF.

Frequently Asked Questions

What is Measurement Uncertainty?

Measurement uncertainty is a quantified range around a result within which the true value is expected to lie with a stated confidence.

Is uncertainty the same as error?

No. Error is the difference from the true value; uncertainty is the doubt about the result.

What is the GUM?

The Guide to the Expression of Uncertainty in Measurement, JCGM 100.

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