The Tropospheric Ultraviolet-Visible (TUV) model, version 4.2 developed by Madronich (2003) was used to estimate the extent of ultraviolet (UV) exposure of general population in Croatia over the summer. Solar noon values (13 h local time, CEST) of the ultraviolet index (UVI) for the period April to October 2004 were calculated for 61 cities in Croatia. The results showed that the risk of sunburn at 13 h local time in clear weather was high between April and September (UVI > 7) and very high in July (UVI > 10). In July, the UVI exceeded 8 between 11 h and 15 h local time. In this study, we developed a simple approximate formula to estimate UVI. The formula includes data on the time, date, altitude and clouds. The difference between our estimate and the TUV model for the summer months of June, July and August at 10 h to 16 h local time was less than 10%.