The so-called “Grand K” kilogram, a cylinder of polished platinum-iridium alloy that has been the world’s sole true kilo since 1889, is to be retired.
Nations gathered in Versailles, west of Paris, are expected on Friday to instead approve the use of a scientific formula to define the exact weight of a kilogram.
The change will have no discernable impact for most people. Their bathroom scales won’t get kinder and kilos and grams won’t change in supermarkets.
But scientists are hailing the vote as a mini-revolution in the field of weights and measures, which underpins vital human activities like international trade.
And it will mean redundancy for the Grand K and its six official copies.