Integration of Beef CRC research results with an established animal growth model (Davis Growth Model) has improved the prediction of live animal performance and carcass composition at slaughter. This paper describes the BeefSpecs fat calculator developed to assist beef producers meet market specifications. The prediction of P8 fat depth in BeefSpecs has been developed by simulations using the Davis Growth Model. BeefSpecs reports final live and carcass weights and predicts P8 fat thickness, using inputs of initial liveweight, frame score, current P8 fat depth, expected average daily gain, feed type (grain or pasture), time on feed and use (or not) of growth promoters, as well as an assessment of activity (feedyard, small or large paddocks). Initial evaluation trials showed close agreement between the predicted fat depth and actual measurements, indicating the ability of the tool to predict mean final P8 with a reasonable degree of accuracy. Plans for the development of an 'optimisation model' and a 'steer performance model' are also briefly described.