ISO/IEC Guide 98-3:2008/Amd 1:2026

• Status: Published
• Publication Date: 26-Jul-2026
• ICS: 17.020 - Metrology and measurement in general
• Technical Committee: ISO/TMBG - Technical Management Board - groups
• Drafting Committee: ISO/TMBG - Technical Management Board - groups
• Current Stage: 6060 - International Standard published
• Start Date: 27-Jul-2026
• Due Date: 13-Aug-2028
• Completion Date: 27-Jul-2026

• Amends: ISO/IEC Guide 98-3:2008 - Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in measurement (GUM:1995)
• Effective Date: 16-Aug-2025

Overview

ISO/IEC Guide 98-3:2008/Amd 1:2026 is an internationally recognized amendment to the core guidance on the expression of uncertainty in measurement (GUM:1995). Published by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC), this amendment specifically addresses the handling of nonlinearity in measurement models when evaluating measurement uncertainty. This guide ensures that measurement results are comparable and meaningful across scientific, industrial, and regulatory fields worldwide.

Key Topics

• Nonlinearity in Measurement Models
  The amendment focuses on the identification and treatment of significant nonlinearities that affect measurement uncertainty analysis. For many real-world measurement systems, relationships between variables are not strictly linear, making this guidance critical for accurate uncertainty estimation.

• Use of Monte Carlo Methods
  When nonlinearity is significant, the amendment recommends using Monte Carlo methods, as detailed in JCGM 101:2008, to better estimate uncertainty distributions. This approach provides a robust alternative to linearization techniques in complex measurement models.

• Higher-Order Taylor Series Expansions
  The amendment outlines the need to consider higher-order terms in the Taylor series expansion of the measurement function. Inclusion of these terms becomes essential when linear approximations are insufficient for describing the system's behavior.

• Augmented Uncertainty Calculations
  For significant nonlinear effects, both the estimate of the quantity of interest and the combined standard uncertainty must be recalculated to incorporate second-order and possibly higher-order influences.

• Bibliographic References
  The document updates the related bibliography to include references to supplementary guidance, such as JCGM 101:2008 on the propagation of distributions using Monte Carlo methods.

Applications

This amendment is valuable across multiple domains where measurement uncertainty has a substantial impact:

• Calibration and Testing Laboratories
  Ensures laboratories can deliver accurate and credible measurement results, specifically when nonlinearity is present in calibration processes.

• Quality Assurance and Metrology
  Supports organizations in demonstrating competence and compliance with international measurement standards, essential for ISO/IEC 17025 accreditation.

• Scientific Research
  Assists researchers in assessing and reporting measurement uncertainty, leading to more reproducible and trusted outcomes.

• Industrial Measurement Systems
  Provides manufacturers, especially those dealing with advanced sensors and automation, with tools for rigorous uncertainty evaluation in nonlinear measurement models.

Related Standards

For more comprehensive guidance on measurement uncertainty and related methodologies, consult the following standards:

• ISO/IEC Guide 98 Series

  • Guide 98-1: Introduction to the expression of uncertainty in measurement
  • Guide 98-2: Concepts related to measurement uncertainty
  • Guide 98-3:2008: Main guide to the expression of uncertainty in measurement (GUM:1995)
  • Guide 98-4: Role of measurement uncertainty in conformity assessment
  • Guide 98-6: Developing and using measurement models

• JCGM Documents

  • JCGM 100:2008 - Evaluation of measurement data: Guide to the expression of uncertainty in measurement
  • JCGM 101:2008 - Supplement 1: Propagation of distributions using Monte Carlo methods
  • JCGM 102:2011 - Supplement 2: Extension to any number of output quantities

• ISO/IEC Guide 99:2007 (VIM)

  • International vocabulary of metrology - Basic and general concepts and associated terms

By incorporating the recommendations in this amendment, users ensure that their uncertainty analyses are robust, transparent, and aligned with the latest international metrological best practices.

Guide 98-3
First edition
Uncertainty of measurement —
2026-07
Part 3:
Guide to the expression of
uncertainty in measurement
(GUM:1995)
AMENDMENT 1: Nonlinearity in
measurement models
Reference number
ISO/IEC Guide 98-3:2026(en) © ISO/IEC 2026

ISO/IEC Guide 98-3:2026(en)
© ISO/IEC 2026
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© ISO/IEC 2026 – All rights reserved
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ISO/IEC Guide 98-3:2026(en)
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© ISO/IEC 2026 – All rights reserved
iii
ISO/IEC Guide 98-3:2026(en)
Joint Committee for Guides in Metrology
Evaluation of measurement data — Guide to the
expression of uncertainty in measurement.
AMENDMENT 1: Nonlinearity in measurement models
Évaluation des données de mesure — Guide pour l’expression de
l’incertitude de mesure. AMENDEMENT 1: Non-linéarité dans les
modèles de mesure
JCGM 100:2008/Amd.1:2026
© JCGM 2026 – All rights reserved
© ISO/IEC 2026 – All rights reserved

ISO/IEC Guide 98-3:2026(en)
ii JCGM 100:2008/Amd.1:2026
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