This calculates water based on lye, not oils. Calculating water to produce the desired solution strength.
When you use less water you soap gets hard faster, soap is ready to use sooner vrs. weeks (discount water cold process) and the bars shrink less.
When I say solution strength meaning the precentage of lye in lye water.
I use 38 - 40% lye solution.
But if its a tricky Fragrance, I go to about 35%