15 foot round? About 5000 gallons, if it's four feet deep. Here's a formula for round pools:
distance across*distance across*depth*5.9
for rectangles:
length*width*depth*7.5
or for a deep end:
length*width*((shallow end depth + deep end depth)/2)*7.5
10,408 gallons.
This pool holds a maximum of about 10,360 gallons of water.
How many gallons will fit into a 24 foot diameter x 4 foot high round swimming pool
7,646.4 gallons are needed.
About 18,402 gallons.
About 24 gallons.
About 14,351 US gallons of water.
5,310 gallons.
The pool holds 7,600 gallons of water
A 16-foot by 32-foot by 4-foot pool can hold up to about 15,320 gallons of water.
1 cubic foot is 7.48 US gallons
Go to http://www.havuz.org/pool-calculators.htm