We present a systematic modelling methodology using the spiral growth mechanism of Burton, Cabrera and Frank to predict the steady-state shape of organic molecular crystals grown from solution. This methodology has been developed to eliminate the need for special modifications for each new crystal system studied. Therefore, the mechanisms and choices for spiral shapes, edges and evolution are mathematically determined as governed by the underlying solid-state chemistry and physics. The power of the approach is demonstrated for several crystal systems: naphthalene grown from both ethanol and cyclohexane; anthracene grown from 2-propanol; and glycine grown from water. The predicted crystal shapes are in good agreement with experiment.