How many gallons of water in a basement of 25 feet by 20 feet if there was 4 feet of water?

It's a common mistake, but you must first find the volume of the pool. Calculate the volume of the pool by surface area X average depth. This will give you the cubic footage (approx.) in the pool. Ft3 X 7.48 (gal/ft3) will give you gallons in pool (approx.).