Well-verified methods for calculating rate of evaporation from swimming pools are not available. A new correlation is presented here which shows good agreement with all available data for partially and fully occupied swimming pools. Data from four studies (all that could be found) are correlated with a mean absolute deviation of 18%. Several other published correlations were also tested against the same data and gave much larger deviations. The new correlation will help in correct sizing of HVAC equipment and performing accurate energy consumption calculations.