weight of bar math help

[deg195]

Hi, I have bars of soap that I hand cut. I want to get a soap cutter and I am trying to figure out which size to get 1 inch or 1 1/4 inch. I currently hand cut my soaps. They are usually between 1 inch and 1 1/4 inch. I have a bar that I like the size is 1 1/4 x 2.5 x 3.5 The weight is 5.7 ounces. when I multiple 1.25 x 2.5 x 3.5 x0.40 I get 4.3. I do not understand why the bar weighs what it does but the math tells me it should be less. Any ideas?
I would like my bars to be about 5 ounces.
Thanks, BArb

 

[DeeAnna]

Your 5.7 ounce bar weight is the weight of the finished soap -- the oils plus lye plus water.

The "0.40" rule gives you an estimate of the weight of the OILS only. The lye and water are not included.

This rule assumes you're soaping with "full water" and normal types of oil blends. It's reasonably accurate unless you're doing something really strange like adding a lot of filler such as making a salt bar (aka spa bar).

Go back to your recipe and look at the oil weight only -- can you make a connection between your recipe and the "0.40" rule now?