when you enter your recipe into the SoapmakingFreinds calculator (LOVE IT) you click "master batch" and the Water:Lye ratio at which you have made your master batch at the top. Then, in the lye section, you input the lye concentration you wish to use - say 33%. NOTE - I make my master batch lye solution at a 50% concentration, or a 1:1 water:lye ratio - be sure to put in the ratio at which you made your master batch. When it calculates your recipe - it will tell you how much additional liquid you need. See (poorly drawn ) circles below. I just threw in 100% olive oil at 500 grams oil weight for illustration. for this - the calcuator tells me to take 128...gms of my master batch, plus 64...gms of additional liquid - as I input a 33% concentration. Watch the numbers change as you change your concentration. LOVE this calculator!