Representatives from 60 countries voted to redefine the International System of Units (SI) for weight, current, temperature and amount of chemical substance.
All the SI units will now be defined in terms of constants that describe the natural world.
It will bring an end to the use of physical objects to define measurement units.
The new definitions impact four of the seven base units of the SI:
The kilogram, ampere, kelvin and mole; and
All units derived from them, such as the Volt (V), ohm (Ω) and Joule (J).
The definition of the kilogram will now be replaced by the Planck constant – the fundamental constant of quantum physics.
Until now, it has been defined as the mass of a platinum-iridium lump, the so-called Grand K, that is kept in a secured vault on the outskirts of Paris.
It has been the world's one true kilo, against which all others were measured, since 1889.
The decision has been made at the General Conference on Weights and Measures in Versailles, France, which is organised by Bureau of Weights and Measures (BIPM).