About 7300 gallons
If 20' is the circumference, then the answer is 833.4 gallons.
Approximately 4,400 gallons.
To calculate this the depth would also be needed
I would say probably around 50-200 gallons.
To fill your 18-foot round pool to a depth of 48" would require about 7,646 gallons of water. If you filled it to 36", the total would decrease to about 5,735 gallons.
There are 13,536 gallons in a 24 foot diameter pool that has 4 feet of water. Not true for a pool that is 4 feet in height. This would hold less than 4 feet of water.
An 8-foot round pool filled to a depth of 13 inches would contain about 410 gallons of water.
A 15-foot round pool with 52 inches of water is holding about 5,750 gallons. If the water is only 48" deep, the pool would be holding around 5,310 gallons.
Cant work it out without the depth and do you really mean 20 inch by 40 inch? that's tiny.
It would fill about 91,000 residential in-ground swimming pools.
A 100-foot round pool filled with 1.5 feet of water would be holding about 88,500 gallons.
The area of the pool would be 1440 cubic feet. There are 7.4805 gallons per cubic foot. Doing the math, there would be 10771.92 gallons of water in your 15 X 24 X 4 foot swimming pool.
This would be about 15,611 gallons of water.
About 7614 gallons.
A 28-foot round pool filled with 4 feet of water would contain about 18,500 gallons.
how many ounces do of roundup do I mix with two gallons of water?
If you filled the pool to a depth of 48 inches, the total volume would be about 21,240 gallons of water.
If it is a round 18' in diameter and a constant 52" deep then the volume is 158.6 gallons per inch. 52 inches would then be 8247.2 gallons.
Kiloliters or gallons depending on sizeo f the pool.