**Gravitational mass** is the mass of a body which determines the magnitude of gravitational pull between the body and the Earth This is determined with the help of a beam balance. According to Newton’s law of gravitation, the gravitational force on a body is proportional to its mass. We can measure the mass of a body by measuring the gravitational force exerted on it by a massive body like Earth.

If F_{A} and F_{B} are the gravitational forces of attraction on the two bodies of masses m_{A} and m_{B} due to the Earth, then;

**F _{A} = Gm_{A}M/R^{2} and F_{B} = Gm_{B}M/R^{2}**

where M is mass of the Earth. R is the radius of the Earth and G is the gravitational constant.

**So, m _{A}/ m_{B} = F_{A}/F_{B}**

If one of the two masses is a standard kilogram, the unknown mass can be determined by comparing the gravitational force.