What's 16x16 round? Do you mean 16 foot diameter and 16 feet deep? Somehow I doubt that is what you meant -- never heard of a 16 foot deep pool except for diving. A round pool would be a cylinder, so the volume is the area of the surface times the depth. The area of a circle is pi times the square of the radius (pi * r2). If the pool is 16 feet across (diameter), then the radius is 8 feet. The surface area is then 3.14159 * 82 == 201.1 Square feet. Multiply that by the depth and you have the volume in cubic feet. If it's 4' deep, then you'd have about 804 cubic feet of water. A cubic foot is about 7.5 gallons, so 804 cubic feet would be about 6030 gallons.Another way to calculate it would be about 1500 gallons per foot of depth for a 16 foot diameter pool.
