How is mass measured other than just converting from weight?
First, the kilogram (kg) unit of mass is defined by the mass of the special cylinder made in the Platinum and Iridium as you can see in the figure to the right. You can measure mass even in space, far away from any gravitational field simply by applying a known force (using, for an example, a spring) to the object and measuring its acceleration. From these, we know that m = F/a.
