The cooling of moulds through the usage of baffles is commonplace in the plastic injection moulding industry. The flow of cooling water through the baffle entrance experiences a sharp 90° bend as well as a circular-to-semicircular geometry change. As it is apparent from the literature that no pressure loss relationships are available, an experimental test rig was constructed to enable these losses to be measured. Furthermore, a numerical model was constructed through the use of computational fluid dynamics to assist in the development of these correlations. This paper discusses this flow problem and develops a new empirical correlation using dimensional analysis for the sharp circular-to-semicircular elbow entrance of the cooling baffle of a plastic injection mould. It was found that the empirical relationship predicts the pressure losses with good accuracy.