Attention not to confuse mass and weight.
The mass (kg) is a intrinsic characteristic of the body and
is measured in kilogram.
Masse spécifique ou volumique = quotient de la masse
d'un corps par son volume.
Specific mass = quotient of the mass of a body by its volume
Weight is a force which depends on terrestrial attraction
and it is the equivalent of the mass of a body by the acceleration
of gravity (9.80665 at the sea level) and is measured in Newton
[ N ].
For example a man of 75 kg (it is its mass, and not its weight
contrary to the current expression), has a weight of: 75 *
9.80665 = 735,5 N on the sea level.