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
so in your case, 15*26*4.3*7.5=12500 gallons
18,506 U.S. gallons
How large is the pool? In ground or above ground? Shape? Above ground is easier to calculate. I have an oval above ground pool which is 18 x 38. It holds approx. 15,000 gallons. To get an accurate answer, you need to be far more specific.
10053.82 gallons (US) 8371.568 gallons (UK)
6015.77 gallons
319.2 gallons for every inch the water in it is deep.
A round pool that is 16 feet across and is filled with 48 inches of water will contain about 6,041 gallons of water.
Just a little over 6,000 gallons.
13,346 gallons per vertical foot.
(18 x 48) / 7.48=115.5
5300 Gal
15000 gallons
18,000