Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

NIST Technical Note 1297

1994 Edition (Supersedes 1993 Edition)

Web Version History

Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results

Barry N. Taylor and Chris E. Kuyatt

Brief summary

A method of evaluating and expressing uncertainty in measurement adapted from NIST Technical Note 1297.

TN 1297 also available as a PDF file

To view documents which are "pdf files," Adobe Acrobat Reader is required. This software may be downloaded without charge.


(Cover page)

Preface to the 1994 Edition
1. Introduction
2. Classification of Components of Uncertainty
3. Type A Evaluation of Standard Uncertainty
4. Type B Evaluation of Standard Uncertainty
5. Combined Standard Uncertainty
6. Expanded Uncertainty
7. Reporting Uncertainty
8. References
   A: Law of Propagation of Uncertainty
   B: Coverage Factors
   C: Statements of Uncertainty Associated with Measurement Results
D: Clarification and Additional Guidance
D.1 Terminology
D.2 Identification of uncertainty components
D.3 Equation (A-2)
D.4 Measurand defined by the measurement method; characterization of test methods; simple calibration
D.5 tp and the quantile t1-α
D.6 Uncertainty and units of the SI; proper use of the SI and quantity and unit symbols
D.7 References


Created July 6, 2009, Updated November 25, 2019