How much can you carry? A study in capacity modelling.

In the simplest terms, when we think about capacity, we think about how much of something that we have. The ‘something' can be any quantity - time, volume, weight, etc. The capacity of a machine that makes widgets (or sausages) can be calculated simply by the number of widgets (or sausages) it can make in a specified period of time. In contrast, a person's capacity, in particular our capacity to do useful work, is a little more complicated than that.