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International Legal Metrology FAQs

Legal metrology is the practice and process of applying statutory and regulatory structure and enforcement to metrology. 

Legal metrology covers trade (e.g., consumer protection), health, safety, and environmental protection. Regulations relating to these areas set measurement-based requirements and requirements for measuring instruments used for such purposes. 

Learn more about Legal Metrology (and how it differs from Weights and Measures) here.

The International Organization of Legal Metrology (OIML) is an intergovernmental treaty organization. Its mission is to enable economies to put in place effective legal metrology infrastructures that are mutually compatible and internationally recognized for all areas for which governments take responsibility, such as those that facilitate trade, establish mutual confidence, and harmonize the level of consumer protection worldwide.

For information, please visit the OIML website

OIML Recommendations are model regulations on weighing and measuring instruments, physical standards, prepackages and measuring procedures for use in legal metrology applications. OIML Member States are obliged to implement these Recommendations as far as possible.

OIML Guides provide guidance on a variety of topics, such as uncertainty calculation, verification equipment, density measurement, and Electric Vehicle Supply Equipment.

NIST OWM represents the U.S. legal metrology system in the international metrology community since the U.S. Senate ratified the International Organization of Legal Metrology (OIML) Treaty in 1972. 

The International Legal Metrology group within OWM serves as the primary representation of the U.S. in international legal metrology organizations and other international forums related to weights and measures. 

OWM staff also coordinate the participation of U.S. manufacturers, users of weighing and measuring instruments, legal metrology officials, and other U.S. stakeholders in the technical work of OIML by circulating draft Recommendations and other OIML publications for comment and by leading U.S. delegations to OIML Technical Meetings.

Although the U.S. is a participating member for a range of OIML Recommendations, the U.S. has only partly implemented these Recommendations. Weighing and measuring instruments used for trade must comply with the requirements in NIST Handbook 44.

National Type Evaluation Program (NTEP) operates under the responsibility of the National Conference on Weights and Measures (NCWM) and provides Certificates of Conformance based on a successful completion of a weighing or measuring instrument (i.e., device) evaluation based on the technical requirements in NIST Handbook 44

The OIML Certification System (OIML-CS) is the OIML-based system for issuing, registering, and using certificates and associated type evaluation and/or test reports for a range of measuring instruments that are based on the requirements of OIML Recommendations.

No. NTEP does not accept OIML certificates as the basis for an NTEP Certificate of Conformity. However, for certain devices (currently only load cells) NTEP does issue NTEP Certificates of Conformity based on OIML test results.

In general, NTEP certificates are not valid outside the U.S., with the exception of load cells, for which Canada accepts NTEP Certificates of Conformity. Canada also accepts test results of NTEP evaluations of certain fuel dispensers and scales to issue a Canadian Notice of Approval. Other countries that are known to have accepted NTEP test results in the past are Saudi Arabia and Colombia.

(Please note that even if a country is known to accept NTEP test results, acceptance of NTEP Certificates of Conformity or NTEP test results is not guaranteed. The certificate or test results must prove compliance with the local legislation and regulations.)

Visit the NCWM website for more information on the U.S./Canada Mutual Recognition Arrangement.

Below is a list of contacts for type approval of a weighing or measuring instrument:

Country/ EconomyCertification bodyAdditional information
CanadaMeasurement Canada 
MexicoNational Metrology Center (CENAM) 
EuropeAny European Notified BodyAn overview of Notified Bodies can be found on the EU website.
UKAny UK Approved BodyVisit the UK website to find a UK Market Conformity Assessment Body.
AustraliaNMI Australia 

A Regional Legal Metrology Organization (RLMO) is an organization of national legal metrology institutes in a certain geographic region of the world with the objective of promoting regional cooperation in metrology issues. The U.S. participates in SIM (NORAMET) and APLMF.

RLMOAcronym/LinkNumber of members
Intra-Africa Metrology SystemAFRIMETS

47 principal members in 6 sub-RMOs:


Asia-Pacific Legal Metrology ForumAPLMF21 full members
Euro-Asian Cooperation of National Metrological InstitutionsCOOMET17 members
Gulf Association for MetrologyGULFMET6 members
Inter-American Metrology SystemSIM5 sub-RMOs: NORAMET (3), CARIMET (13), CAMET (6), ANDIMET (5), AND SURAMET (5)
European Cooperation in Legal MetrologyWELMEC38 members

NIST OWM participates in multiple working and task groups, committees, etc. in regional, national and international organizations to facilitate and guide the development of numerous documentary standards related to weighing and measuring equipment, utility meters (e.g., water, gas, electric), package labeling related to both the quantity and quality of products, and environmental protection:

ISOInternational Organization for Standardization
OIMLInternational Organization of Legal Metrology
BIPMInternational Bureau of Weights and Measures
AWWAAmerican Water Works Association
ANSIAmerican National Standards Institute
NCSLINCSL (National Conference of Standards Laboratories) International
NCWMNational Conference on Weights and Measures
RWMAsU.S. Regional Weights and Measures Associations (WesternCentralSouthernNortheastern )
IECInclusive Engineering Consortium
AGAAmerican Gas Association
AAMIAssociation for the Advancement of Medical Instrumentation
ASTM InternationalAmerican Society for Testing and Materials
Created June 20, 2024, Updated July 18, 2024