Yep. I have a mold that is 8 inches long, 3.5 inches wide and 2.5 inches deep. This is a silicone loaf and to pour even to the top, I would multiply 8 x 3.5 x 2.5 = 70. 70 x 0.4 = 28 ounces of oil for my 8 inch long 40-44 ounce capacity mold, with the full water amount. Since I'm new to soaping (5 batches so far), I only used a water discount (40% lye concentration) when I made my castile since they take a long time to reach trace with the full water lye concentration.
I think the 0.4 multiplication is to find out the amount of oils, not the total volume. My wood log mold is 10 inches long, and that's what I used for my castile. Comes out to (10 x 3.5 x 2.5 / .4) 35 oz of oil then the 40% lye solution and it filled it almost to the top with no overflow.
So length x width x height of pour space (the interior of the mold, not the outside of it). Multiply by 0.4 to get the amount of oils for your mold. Take the amount of oils for your mold, plug into your lye calculator (I am a SoapCalc person), and view your recipe to get your water & lye amounts.
A good way to figure out how to resize your batch is once you see a recipe you like, put the recipe in your lye calculator using the amounts, and then look at the percentages the calculator gives you. Adjust your percentages to what you like. Then when you're ready, you can set the amount of oils required for YOUR mold, then just put in percentages and the calc will give you the actual amount of oils you need for that size.
I'm not sure I just made sense
