Cannot be answered with only these measurements. You need to specify what shape the pool is. Also, for a rectangular pool, the length, width and depth are needed. For a round pool, the diameter and depth are needed.
5284.62 gallons
If 20' is the circumference, then the answer is 833.4 gallons.
6015.77 gallons
70
5300 Gal
18,000
How many gallons of water for a 15'x30' swimming pool?
13,346 gallons per vertical foot.
It is 30.6 cubic feet = 190.3 Imperial gallons.
18,770 Gallons or round it up to 20,000 for calculation purposes.
'bout 1500 to 2000
There is NO way to calculate this without knowing how deep the pool is filled!