Current Edition Checked October 24, 2026
The 2008 text remains the reference, with a 2026 amendment; supplements cover Monte Carlo propagation and multivariate models.
What It Covers
The internationally agreed method for evaluating and expressing uncertainty in measurement, so results from different laboratories can be compared.
Who It Applies To
Calibration and testing laboratories, and anyone stating a measurement result with its uncertainty.
Key Requirements
- A measurement model relating the result to each input quantity.
- Type A (statistical) and Type B (other information) evaluations of standard uncertainty.
- Combination of standard uncertainties, including correlations, into a combined standard uncertainty.
- An expanded uncertainty with its coverage factor, reported with the result.
What an Auditor Asks to See
- The uncertainty budget for a reported result, and where each contributor came from.
Where Systems Fall Short
- Budgets that list contributors but ignore correlations.
- Coverage factors applied without considering degrees of freedom.
How QES Helps
Uncertainty budgets reviewed term by term, and rebuilt where the model is wrong.
Related Standards
Sources. BIPM — Joint Committee for Guides in Metrology (opens in a new tab). Status checked October 24, 2026. This page summarizes GUM · Guide 98-3; it does not reproduce or replace it. Buy the standard from its publisher, or read the regulation in its official text, before relying on a detail. Not legal advice.