Close to 24,000 gal if it is rectangular.
To chlorinate a 20x40 pool, you typically need about 1-3 pounds of chlorine per 10,000 gallons of water to achieve the recommended chlorine level. Assuming an average depth of 4 feet, the pool holds approximately 27,000 gallons of water. Thus, you would require about 2.7 to 8.1 pounds of liquid chlorine to reach the desired levels, depending on the current chlorine concentration and water conditions. Always test the water first and adjust accordingly.
10053.82 gallons (US) 8371.568 gallons (UK)
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.
An 18x54 above ground round pool typically holds around 7,646 gallons of water when filled to the recommended level.
A typical in-ground home pool contains between 20,000 and 30,000 gallons of water.
...What are the dimensions of the pool?
18,506 U.S. gallons
6015.77 gallons
319.2 gallons for every inch the water in it is deep.
This cannot be answered without knowing the depth of the water.
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.