g
gram
Massexact by definition
The gram is one thousandth of a kilogram, exactly, by definition of the prefix. It was originally conceived as the mass of one cubic centimetre of water at the temperature of melting ice, which is why one millilitre of cold water still weighs almost exactly one gram.
| 1 g | 0.001 kg |
Where the unit came from
The gram was the intended base unit of the original 1795 metric system. A one-gram artifact standard would have been too small to machine and compare accurately, so the physical standard was made a thousand times larger and the kilogram inherited the base-unit role. That is the reason the SI has exactly one base unit whose name already carries a prefix.
Solvers that use mass