Relatively simple mathematical models for microwave energy penetration in food products were applied, based on Lambert's law and taking into account internal reflections. With these models direct insight in microwave heating distributions in products with basic geometries and homogenous composition can be gained. Effects of changes in product composition with relation to dielectric properties and changes in product size can be predicted. The model was not designed to give an exact and detailed prediction of temperature distributions during microwave heating. However, it can simulate microwave heating of various food products and be useful for designing heat treatments.