What I meant, by "keep it in your head", is that if you add doses, and then test, you'll get to the point where you know what a reasonable dose of chlorine, acid, or alkalinity is for YOUR pool. That way, if your chlorine is low or your pH high, you can simply add the right dose -- learned by experience -- rather than running into the house (or for your smart phone -- and handling phones while you're handling chlorine tabs is NOT a good idea!!) and checking the calculator.

New forum members sometimes get fixated on various calculators, and become dependent on them, which prevents them from reaching that plateau where, 90% of the time, you know the right dose as soon as you see the test results.