FORMULAS FOR POOL CAPACITY. L = length W = width. SURFACE AREA. Rectangular pool = L x W. AVERAGE DEPTH. CUBIC FEET OF VOLUME (surface area times average depth) POOL GALLONAGE IN CUBIC FEET (cubic foot of water = 7.5 gallons) LIMITED USE POOLS: Required turnover at least every 8 hours (8 x 60 min = 480 min)