The process of hot isostatic pressing is modelled in terms of the various mechanisms of densification and sample shrinkage. Using input data of material type, mean powder size, sample size and shape, as well as the hot isostatic pressing parameters of pressure, temperature, time, etc., a computer program provides output data on time to complete densification, sample shrinkage and mode of densification. It is shown that the program can be used to help optimise the HIP cycle and provide information of sample shrinkage and potential residual stress problems