The aim of function costing is to provide designers with a technique for estimating costs directly from the specification of a product or system. This paper provides function cost information for pressure vessels and rolling element bearings. It is shown that the cheapest pressure vessels are much longer and thinner than vessels in common use, i.e. pipes. The costs of both roller and ball bearings are approximately proportional to their load capacities. For bearings selected on the basis of their fatigue performance, i.e. when the dynamic load rating is used for selection, the most economic bearing is that with the greatest value for the ratio D/d. The effect of not achieving this optimum ratio of D/d is also shown.