How many gallons of water are in an oval pool 20 x 40?

Answer 1

Since imperial gallons are no longer in use, I assume that you mean US gallons. 20 x 40 x 5 gives 4,000 cubic feet. 8.33 gallons per cubit foot will give 33,333 us gallons.

Answer 2

Mine is 20 x 40 but has rounded ends. (Double Roman) Takes 24,500 Gallons.

Answer 3

20 feet across, 10 feet deep - your pool holds about 23,500 gallons of water.