# Need Help with Water/Lye Math!!

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#### Arlo

Supporting Member
I have a CP recipe I want to make but need to scale it down. It only gives amounts in grams; no percentages. For the oils, I know how to figure out the percentages. But for the water and lye, I'm not confident in figuring out the %Lye Concentration or the Water/Lye ratio in order to enter into a calculator. The amounts given are: 248g water and 112g lye. So total lye solution is 360g. I think I need to divide 112 by 360 to get the percentage. That would give me 31%. Is this the correct thought process?

And what would the math be to figure out the water:lye ratio?

Also, is there a way I could've entered these amounts in a lye calculator? Or would the only easy option be Water as Percent of Oil (which I've read is not the best one to use)?
Thanks so much.

Just enter the recipe as-is into the soap calculator. It should give you the percentages right next to the grams.

Change the selected setting to percentages, and enter the size of the batch you want. Done.

That worked great for the oils, thanks. But what about the lye solution? The calculator has to have my input for percentage or ratio, and I don't know what that is in the recipe (unless my calculation of 31% is accurate)?

That worked great for the oils, thanks. But what about the lye solution? The calculator has to have my input for percentage or ratio, and I don't know what that is in the recipe (unless my calculation of 31% is accurate)?
Yes, that is correct insofar that you are trying to exactly dupe the recipe. However, I agree with @dmcgee5034 that 33% is a good starting place, unless you have a specific reason for wanting to use more water.

Thank you both. I was stuck on following the recipe exactly but have no reason to use more water so will try 33%.

It’s also good to let the soap calculator tell you how much lye is needed, based on the oils you entered. There can be typos in any recipe, or you may learn that they are using far more (or less) superfat than you like.

Remember that while the amount of water is variable, the amount of lye for any given recipe is really isn’t, unless you change the superfat.

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