I'm just lazy, when I do confetti soap I just make a normal sized batch and just pour half, add my confetti and fill the rest of the mold. If I have extra soap batter left over I just pour it into one of my single bar molds. It's not like having extra soap bars is a bad thing. If I don't sell them to someone then I just use them myself. Calculating the difference is just too much work when I just want to make soap. And all of the soap I make is goat milk soap and has basically the same oils and ingredients so my confetti ingredients are listed already.