Everyday things are easily taken for granted: the alarm that wakes us in the morning at the right time, having enough oats for breakfast thanks to accurate labelling of the package weight, and being able to understand a colleague’s lab results because they didn’t use their own personal set of units.

Credit: Image courtesy of the BIPM

We owe the benefits of modern metrology to the signing of the Metre Convention on 20 May 1875 in Sèvres, France, by seventeen nations1. This marked the establishment of the International Bureau of Weights and Measures, which was to “operate under the exclusive direction and supervision of an International Committee for Weights and Measures, itself placed under the authority of a General Conference on Weights and Measures, consisting of the delegates of all the contracting Governments”2.

The Metre Convention lays out the responsibilities of the International Bureau of Weights and Measures, including the conservation of the international prototypes of the metre and kilogram, comparisons between prototypes and national standards, and “determinations related to physical constants for which more accurate knowledge might serve to increase the precision and ensure better uniformity in the fields to which the units mentioned above belong”2.

Its amendments in 1921 included, for example, a broadening of the Bureau’s remit to measurements related to electrical units and their standards. This led to the inclusion of the ampere into the commonly used metre–kilogram–second system of units as a fourth base unit, which came into effect in 1948.

Following the 9th General Conference on Weights and Measures, where the International Committee for Weights and Measures was directed “to make recommendations for a single practical system of units of measurement, suitable for adoption by all countries adhering to the Metre Convention”3, the kelvin and candela were adopted as additional base units in 1954, and the mole in 1971. Although their definitions have changed over the years, these seven base units have remained at the core of the International System of Units. The most recent redefinition4 — of the kilogram, kelvin, ampere and mole — was on World Metrology Day in 2019.

This year’s theme is “Measurements for all times, for all people”, to commemorate the 150th anniversary of the signing of the Metre Convention. The celebrations will include the 2025 World Metrology Day Symposium, which is available to live-stream, followed by a two-day conference. There will also be memorabilia to celebrate the anniversary, including souvenir medals, a commemorative stamp, and vases similar to those given by the French president in 1972 to the countries that participated in the Metre Commission.

To uphold the 2025 motto of World Metrology Day, the General Conference on Weights and Measures passed a resolution in 2022 “to develop a long-term vision for an international measurement system that will remain relevant and adequately address new metrological challenges”. This vision will be presented at the 28th iteration of the meeting in 2026.

In a Comment in this issue, Wynand Louw and Gert Rietveld, president and member of the International Committee for Weights and Measures, respectively, summarize the Committee’s strategy beyond 2030. They highlight efforts to ensure that measurements last “for all times” — such as by a further redefinition of the second — as well as the need to increase adherence to the Metre Convention, which currently has 64 member states and 37 associate states, so that it is indeed “for all people”.

In addition, in this issue’s Measure for Measure, Chingis Kuanbayev, from the International Bureau of Weights and Measures, and Kangyoung Sung, from the Korea Research Institute of Standards and Science, outline the vision of young metrologists for the future of the field beyond 2050, with a particular focus on its challenges and opportunities.

Despite the all-encompassing nature of metrology in our lives, its importance can often be somewhat underappreciated. With the recognition of World Metrology Day as a UNESCO International Day in 2024 (ref. 5), the achievements of metrology will hopefully be more widely appreciated. Maybe at the end of the day, when you set your alarm for tomorrow, you might think about the impacts of metrology and celebrate the legacy of the Metre Convention.