Can't be answered without knowing the depth of the pool.
There are about 7.481 gallons per cubic foot. So if your 24 foot by 48 foot pool is filled 3 feet deep you will need 24 x 48 x 3 x 7.481 = 25,854 gallons of water.
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.
I will assume that you are wanting to know the depth of the water for a 24x48" above ground pool. With the wall being 48" in height, I would usually tell the buyer to subtract 4-6" off of the wall height. So, in the case of the 48" wall, the water level will be anywhere between 42-44". !
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