Units FAQ

In which unit is mass entered?

Answer: Mass must be given in consistent mass units (W/g). Force, length, and temperature are primary units. Mass is then derived from these units secondarily. Accordingly, notable points include the following:

1. Ton represents ton-force (tonf) when the Ton, m, C unit set is chosen.
2. A mass of 1.0 tonm, also known as a tonne or metric ton, is given as 1000 kg. In a standard gravity field, the weight of 1.0 tonm produces 1.0 tonf, or a ton-force, given as 9810 Newtons (N).
3. Because mass must be entered in consistent units (W/g), and not as a force, 1.0 tonf would be entered as W/g = 1 tonf / (9.81 m/s²) = 0.102 tonf * s²/m.

Additional information may be found in the Mass units article and in the CSI Analysis Reference Manual (Joints and Degrees of Freedom > Masses, page 39).