Pool Evaporation Calculator

How It Works

A typical uncovered pool loses about one-quarter inch of water per day to evaporation — that is about 2 inches per week or roughly 500-1,000 gallons per week for an average-sized pool. Evaporation is driven by four factors: the temperature difference between water and air, relative humidity, wind speed, and surface area. Hot water in dry, windy conditions evaporates fastest. A solar pool cover (also called a solar blanket) reduces evaporation by 90-95% and can also raise water temperature by 5-10 degrees. Even a liquid solar cover (a thin chemical layer that floats on the surface) reduces evaporation by about 40%. If your pool is losing more than an inch per day, you may have a leak rather than normal evaporation.