HI, and welcome to the forum!! Once you give the volume of your pool as Watermom requested, we can help you figure out how much to add. In the meantime, I wanted to warn you that you need to handle muriatic acid carefully--wear gloves, eye protection, and above all, stay upwind of the fumes. I can tell you from experience that one good whiff of the fumes from that stuff will make you seriously believe that you'll never breathe again. If it splashes on your skin, just dunk said skin in the pool to wash it off. If you splash it on concrete, even if you wash it, it will pit--so just be very, very careful.