How to Resize a Soap Recipe to Fit Your Mold
Learn how to resize soap recipes to fit your soap mold; includes step by step details plus helpful screenshots.
Most of my recipes are sized to fit a Crafter’s Choice 1501 silicone mold, or a homemade wooden version of similar size.
What if you have a larger or smaller mold, but want to make one of my recipes?
No problem! This article will help you out!
(PS: It looks like a lot of words and a lot of math, but that’s because I’m spelling out every single step in detail. I promise it’s a lot easier than it looks!) 😊
Steps to Resize a Soap Recipe
Step 1: Figure out how many ounces of oil your mold can hold.
The formula for this is:
length x width x height x 0.4
So in the case of my Crafter’s Choice mold (with dimensions of 8 by 3.5 by 2.5 inches), that would be:
8 x 3.5 x 2.5 x 0.4 = 28
This means my Crafter’s Choice mold will hold a recipe containing about 28 ounces of oil, which is why you’ll notice most of my recipes have 28 ounces total oil in them.
Step 2: Find the percentages of oils in the recipe (if they aren’t already provided.)
To start, you need to convert the soap recipe into percentages.
Most of my newer recipes, plus recipes in my ebooks, already have the math done and the percentages provided for you, so in that case, you can just skip this step, however, some of the older ones on this site haven’t been updated yet.
Converting a soap recipe into percentages is quick and easy.
First, you add up the total weight of the oils, then you divide each individual oil by the total amount.
Here’s an example – let’s say your soap recipe contains these oils:
- 14 ounces (397 g) olive oil
- 7 ounces (198 g) coconut oil
- 4 ounces (113 g) cocoa butter
- 3 ounces (85 g) shea butter
Add up the total weight of the oils: 14 + 7 + 4 + 3 = 28 ounces (794 g)
Now, let’s start with olive oil: Divide 14 ounces olive oil by the total amount of oil:
14 divided by 28 = 0.5
0.5 is the same as 50%, so olive oil is 50% of your recipe.
Repeat with the other oils:
- 7 ounces coconut oil divided by 28 ounces total oil = 0.25, which is 25%
- 4 ounces cocoa butter divided by 28 ounces total oil = 0.14, which is 14%
- 3 ounces shea butter divided by 28 ounces total oil = 0.107, which we’ll round to 0.11, which is 11%
The recipe’s oils can now be shown as: 50% olive oil, 25% coconut oil, 14% cocoa butter, 11% shea butter
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Step 3: Take the percentages to a soap calculator.
Once you have percentages available, you can resize easily with a soap calculator. I’m going to use Soapee for this example.
I’m also going to use the recipe from my Make a Simple Homemade Soap article:
- 12 oz (340 g) olive oil (75%)
- 2.5 oz (71 g) coconut oil (15.6%)
- 1.5 oz (43 g) castor oil (9.4%)
- 2.14 oz (60 g) sodium hydroxide (lye) (6% superfat)
- 4.5 oz (128 g) distilled water
And, for this example, let’s say that I want to resize the soap recipe to fit a mold that I calculated (back in step 1) will need 56 ounces of oil.
Once you’ve navigated to Soapee’s lye calculator:
In Box 1, keep the setting for making solid soap.
In Box 2, keep the setting set to percentages, but fill out the total amount of oil that your new mold needs. I want to make the soap fit my larger mold, which holds 56 ounces of oil, so I’ll change that number to 56 ounces.
In Box 3, we’re going to set the water amount. You can leave the number set as it is, but I almost never do that unless I’m making hot process soap. It helps to lower the default amount of water, especially for palm-free soaps, so they firm up faster in the mold. If in doubt, you can rarely go wrong with a 2 to 1 water: lye ratio (this means twice as much water as lye).
To figure the exact water/lye ratio that was used in a particular recipe, just divide the water amount by the lye amount. In my example recipe above, I have 4.5 ounces of water divided by 2.14 ounces of lye = 2.1.
This means I used a 2.1 to 1 water:lye ratio, which will look like this in Box 3:
In Box 4, you can change the superfat. The standard 5% superfat is almost always a safe bet, though your particular recipe may indicate otherwise. In my recipe, I have a 6% superfat listed (though 5% would be completely fine too), so you could change it to that if you’d like.
I just ignore Box 5, because I use my 30 Essential Oils for Soapmaking Printable Chart along with EO Calc to figure out essential oil amounts for my soaps instead of fragrance oils.
In Box 6, you’ll choose the individual oils listed for your recipe, then hit the plus sign beside each one, then on the right of the screen, input the percentage from the recipe.
Here’s what that looks like from my sample recipe above:
olive oil (75%)
coconut oil (15.6%)
castor oil (9.4%)
Now, scroll down and you have your final recipe, ready to print!
As an aside, I recommend making a small batch of any new-to-you recipe and let it fully cure so you can try it out before making larger batches. You might not care for it, or might want to make some tweaks to improve it, and don’t want to be stuck with a lot of unwanted soap!
Once you have a recipe dialed in just as you like it, then you can scale upwards.
You may also enjoy my Handmade Natural Soaps eBook Collection. It contains:
- Handmade Natural Soaps eBook
- Natural Facial Soaps eBook
- All-Natural Milk Soaps eBook
- DIY Specialty Soaps eBook
- Essential Oils In Soapmaking eBook
- Quick Guide to Troubleshooting eBook
- Printable Soap Additives Chart
- Printable Essential Oils for Soapmaking Chart
- Soapmaking Checklist to Keep You Organized
- Reference List of Soapmaking Abbreviations
- Helpful List of Soap Supplies & Resources
I know this sounds persnickety, but are the measurements of your mold internal or external? I ask because I have a large wooden mold. (I know that it’s just an approximate number.) Thanks in advance for your help! Love what you do! 😊
Hi Julie! For my homemade wooden molds, I use the internal measurements, because the mold sides are a lot thicker than my silicone molds. I’m not 100% sure that’s the “official” recommended way, but it works for me! 😊
Thank you for the great tutorial! If the mold holds 56 ounces and the oils are 56 ounces, do we not have to take into consideration the 23.21 ounces of water and lye? Does it all still fit in the mold? Love your books and recipes!
Hi Luanne! Yes, you’re exactly right! That’s why we take the length x width x height, but then multiply that amount by 0.4 (or 40%). You aren’t calculating the full amount for oils, just 40%.
I really enjoy these Tuesday tips. Thank you!
Hi Deborah, Yay! I’m so happy to hear that! ❤
Jan, do you have any tips for sizing the cute-shaped silicon molds, like the rose-shaped or animal-shaped ones?
Hi Ahsa, That’s such a great question! I’ll be honest, I just usually line up the mini molds I want to use, then have a bunch of other small molds on standby to fill as needed with leftover batter.
I feel like there’s probably some math we could do to be more precise – perhaps try filling each mold with water and seeing what the total volume is?
So if your combined mini molds hold 14 ounces of water total, then aim for your soap batch to weigh 14 ounces total. (Lye + water + oils = total weight)
It still won’t be precise since water will weigh differently than soap batter, but it might get you somewhat closer to making the right amount of soap.
(This is my best guess off the top of my head – someone smarter than me might come in and have a different/better idea.) 😊
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