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.
A 100-foot round pool filled with 1.5 feet of water would be holding about 88,500 gallons.
It would fill about 91,000 residential in-ground swimming pools.
7,646 gallons.
All you have to do to find the volume of a swimming pool is multiply the length x width x average depth x gallons in a cubic foot (7.48). In your case it would be 38x22x5.5x7.48=34,393 gallons.
A 28-foot round pool filled with 4 feet of water would contain about 18,500 gallons.
Go to http://www.havuz.org/pool-calculators.htm
To make 125 gallons of round-up with the same concentration, you would need to use 1.04 gallons of concentrate (125/300 * 2.5 = 1.04).
Liters or cubic meters are typically used to measure the volume of water in a swimming pool.
you would need to know the height of the pool too.
If you filled it all the way to the top (40") it would hold about 2,830 gallons of water.