# How to figure how much oil for mold. ### Help Support SoapMakingForum: #### JazzKitten

##### Active Member
hey paul, thanks for the helpful thread!!..

just curious, where does the .40 come from??
It will be to do with the density of oil. For instance, 1 cubic metre of water weighs one tonne, 1 litre of water weighs one kilogramme. So the volume calculation that Paul has given has the volume of the mould multiplied by 0.4 because I oil is heavier than water - also it's given in inches so that constant of 0.4 will account for the weight conversion to ounces.

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#### earlene

##### Grandmother & Soaper
Lifetime Supporter
One caveat: In spite of this standardized conversion formula for determining how much oil to use when making soap batter to fit into a specific mold, it does not take into account any variables for lye concentration, which can alter the amount of water (or water replacement), which in turn will alter the total batch weight (and density or volume) of your raw soap. Nor does it take into account additional additives and their density, as when one adds pumice or salt, etc. to the batter. All these sorts of things will alter the final total density of your soap and it may be a greater or lesser volume than will fit your mold to the particular depth you thought it would, remembering that neither volume nor density are the same thing as weight.

And there is one other factor that alters density of a substance, and that is heat. Heat causes many substances to expand, including soap, so the same recipe may produce a larger volume when hot than when cold.

Not to burst anyone's bubble about a tried-&-true formula for determining how much oil to use when altering a soap formula to fit a particular mold. But as many a soaper has discovered, sometimes the formula doesn't always produce the amount of batter we thought would fit the mold perfectly and sometimes it falls short, while other times we need a back-up mold to put the extra batter into, such as an individual mold or two.

• AliOop and Zany_in_CO

#### stephswan

##### Member
Hi all, a little late to the game, and I probably should just start a new thread, but I found the formulas in this thread helpful, so just want to double check I'm doing the math correctly for my individual silicone molds:

I have a cloud mold (12 in total), so i poured water in 1 and got: 2.2 fl oz.
2.2 FL oz x 12 (number of molds) = 26.4 fl. oz
Then 26.4 x .554 (to transfer into cub in) = 14.63
14.63 x .4 (the magic number of calcing oils) = 5.85 oz of oil needed for this mold

this is math correct? just seems like such a small bit of oil.

#### SoapDaddy70

##### Well-Known Member
Hi all, a little late to the game, and I probably should just start a new thread, but I found the formulas in this thread helpful, so just want to double check I'm doing the math correctly for my individual silicone molds:

I have a cloud mold (12 in total), so i poured water in 1 and got: 2.2 fl oz.
2.2 FL oz x 12 (number of molds) = 26.4 fl. oz
Then 26.4 x .554 (to transfer into cub in) = 14.63
14.63 x .4 (the magic number of calcing oils) = 5.85 oz of oil needed for this mold

this is math correct? just seems like such a small bit of oil.
I do not think your second equation is correct. Once you get the total volume in fluid ounces you should be multiplying that number by 1.8 to get your cubic inches and then multiply by the .4. So it would be.
26.4 x 1.8 = 47.52 cubic inches
47.52 x .4 = 19 oz of oil needed

#### stephswan

##### Member
I do not think your second equation is correct. Once you get the total volume in fluid ounces you should be multiplying that number by 1.8 to get your cubic inches and then multiply by the .4. So it would be.
26.4 x 1.8 = 47.52 cubic inches
47.52 x .4 = 19 oz of oil needed
THANK YOU!!! I was thinking the final oils looked way too light.

• SoapDaddy70