The application of a simple three‐parameter fit to the temperature dependence of semiconductor band gaps is justified on both practical and theoretical grounds. In all trials the fit is numerically better than that obtained using the widely quoted Varshni equation. The formula is shown to be compatible with reasonable assumptions about the influence of phonons on the band‐gap energy. Approximate analytical expressions are derived for the entropy and enthalpy of formation of electron‐hole pairs in semiconductors.