http://www.havuz.org/pool-calculators.htm
To calculate the volume in gallons of a round pool, do the following calculation: diameter x diameter x depth x 5.9 Example: 28ft x 28ft x 4ft x 5.9 = 18,502.4 gallons
How many gallons of water for a 15'x30' swimming pool?
This pool can hold a maximum of about 5,707.6 gallons of water.
This pool, when filled with 4.5 feet of water, will contain about 15,300 gallons of water.
http://www.havuz.org/pool-calculators.htm
To calculate the volume in gallons of a round pool, do the following calculation: diameter x diameter x depth x 5.9 Example: 28ft x 28ft x 4ft x 5.9 = 18,502.4 gallons
To answer your question you also need to give depth.
How many gallons of water for a 15'x30' swimming pool?
There are 7,985.76 gallons of water in a 1799.5 cubic feet pool.
A pool of this size can hold up to about 11,970 gallons of water.
A pool this size can hold up to about 5,250 gallons of water.
This pool can hold a maximum of about 5,707.6 gallons of water.
This pool, when filled with 4.5 feet of water, will contain about 15,300 gallons of water.
600,000 gallons
48,000 gallons of water
The Shamu Close up pool is 1 million gallons