Guidance

Weights and measures: Legal Metrology

Information for businesses.

• From: Office for Product Safety and Standards
• Published: 20 July 2022
• Last updated: 18 February 2025 — See all updates

The Office for Product Safety and Standards (OPSS) is a world leader in Legal Metrology – the application of legal requirements to measurements and measuring instruments. It supports local government through its purpose-built laboratories in Teddington and upholds its statutory duties.

Our services

OPSS provides statutory calibration under the Weights and Measures Act 1985 and the Coinage Act 1971 on behalf of the Secretary of State. It checks the accuracy of the mass, length and volume of local standards held by local authorities and the UK’s coin standards for the Royal Mint. It also holds the trial plates for the UK hallmarking assay offices.

Read about our calibration service

OPSS, as the Secretary of State, and in relation to UK regulations under Section 12 of the Weights and Measures Act 1985, issues certifications for cubic measures, intoxicating liquor measuring instruments, dynamic axle weighers, and weighing instruments not using the action of gravity (for example gyroscopic NAWI) and used for legal purposes.

The equipment in the laboratories at our Teddington site is fully traceable to national standards and operated in accordance with ISO/IEC 17025:2017.

Access the lists of UK national certificates

Until 30 April 2022, OPSS published NMO branded certificates on GOV.UK under the Measuring Instruments Regulations 2016, or the Non Automatic Weighing Instruments Regulations 2016, or for EEC type examination. These certificates are no longer updated by OPSS. Legacy GOV.UK pages containing those certificates were unpublished on 20 July 2022. However, they remain available for reference and as a matter of public record on the National Archives.

Access the legacy NMO MI certificates – National Archives website

Access the legacy NMO NAWI certificates – National Archives website

Access the legacy NMO EEC certificates – National Archives website

Local Authorities should contact opss.enquiries@businessandtrade.gov.uk to request copies of current/expired S.12 Pattern Approval Certificates.

Contact OPSS

For local authority enquiries please email lau.opss@businessandtrade.gov.uk.

For all other enquiries please email opss.enquiries@businessandtrade.gov.uk.

Write to:

Office for Product Safety and Standards
Stanton Avenue
Teddington
Middlesex
TW11 0JZ

Published 20 July 2022
Last updated 18 February 2025 + show all updates

1. 18 February 2025

   Information updated.

2. 20 July 2022

   First published.