Resolution 6 of the 11th CGPM (1960)

Definition of the metre

The 11th Conférence Générale des Poids et Mesures (CGPM),

considering

• that the international Prototype does not define the metre with an accuracy adequate for the present needs of metrology,
• that it is moreover desirable to adopt a natural and indestructible standard,

decides

1. The metre is the length equal to 1 650 763,73 wavelengths in vacuum of the radiation corresponding to the transition between the levels 2p₁₀ and 5d₅ of the krypton 86 atom.
2. The definition of the metre in force since 1889, based on the international Prototype of platinum-iridium, is abrogated.
3. The international Prototype of the metre sanctioned by the 1st CGPM in 1889 shall be kept at the BIPM under the conditions specified in 1889.

DOI : 10.59161/CGPM1960RES6E

NOTE

This definition was abrogated in 1983 by the 17th CGPM (Resolution 1).