Iran is situated in a region of the world where the solar radiation intensity is considerably high. In some parts of Iran there are more than 200 sunny days. At the same time the need for the production of fresh water from sea water is considerable in the same regions. In this study, a solar still is mathematically simulated and the rate of production of fresh water from sea water is calculated as a function of different meteorological parameters and the solar still specifications. As a special case, some experiments have been done in Shiraz which is located in the south-west of Iran. The experimental and calculated results are in good agreement.