This Guide establishes general rules for evaluating and expressing uncertainty in measurement that are intended to be applicable to a broad spectrum of measurements. The basis of the Guide is Recommendation 1 (CI‑1981) of the Comité International des Poids et Mesures (CIPM) and Recommendation INC‑1 (1980) of the Working Group on the Statement of Uncertainties. The Working Group was convened by the Bureau International des Poids et Mesures (BIPM) in response to a request of the CIPM. The ClPM Recommendation is the only recommendation concerning the expression of uncertainty in measurement adopted by an intergovernmental organization.

This Guide was prepared by a joint working group consisting of experts nominated by the BIPM, the International Electrotechnical Commission (IEC), the International Organization for Standardization (ISO), and the International Organization of Legal Metrology (OIML).

The following seven organizations* supported the development of this Guide, which is published in their name:

  BIPM: Bureau International des Poids et Mesures
  IEC: International Electrotechnical Commission
  IFCC: International Federation of Clinical Chemistry**
  ISO: International Organization for Standardization
  IUPAC: International Union of Pure and Applied Chemistry
  IUPAP: International Union of Pure and Applied Physics
  OlML: International Organization of Legal Metrology

Users of this Guide are invited to send their comments and requests for clarification to any of the seven supporting organizations, the mailing addresses of which are given on the inside front cover***.

*   Footnote to the 2008 version:
In 2005, the International Laboratory Accreditation Cooperation (ILAC) officially joined the seven founding international organizations.

**   Footnote to the 2008 version:
The name of this organization has changed since 1995. It is now:
IFCC: International Federation of Clinical Chemistry and Laboratory Medicine

***   Footnote to the 2008 version:
Links to the addresses of the eight organizations presently involved in the JCGM (Joint Committee for Guides in Metrology) are given on