information:filtering, structural:expansion
Definition

The kilogram is defined in terms of three defining constants:

The formal definition according to the General Conference on Weights and Measures (CGPM) is:

The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 × 10 when expressed in the unit J⋅s, which is equal to kg⋅m ⋅s, where the metre and the second are defined in terms of c and Δ ν.

Defined in term of those units, the kg is formulated as:

This definition is generally consistent with previous definitions: the mass remains within 30 ppm of the mass of one litre of water.