That is all I ever do is guess, I have gotten pretty good at it too. But I am heading to Walmart here after a while for another batch of bleach so I may pick up a measuring cup and I would like to start keeping track of things. The MA scares me too, especially now with one eye, I am healing with the other one, but I tell you not having one is aweful, and not having any would be unbearable, protect your eyes at all costs. This stuff is Hydrochloric Acid, very potent stuff.