At least your math should be easy.
An 18'x4' above ground round pool should be approx. 6000 gallons. 1 gallon of 6% strength bleach should add 10 ppm of chlorine, if I'm mentally moving decimal points correctly.
So if you need to achieve a 25ppm rise in chlorine, it would take 2 1/2 gallons of bleach, etc.