How To Calculate The Amount of Ingredients You Need in Soap Making

How To Calculate The Amount of Ingredients You Need in Soap Making

One of the things that I noticed before I started making my own soap is that most recipes out there are formulated to create a big batch of soap, which is not a commitment you want to make when starting out. Those soap makers share great recipes but they might be a bit difficult to grasp for those with no experience in soap making that don’t even know how to start.

So, here is the question: how do you know how much of each ingredient do you need to make one or two soap bars?

Fear no more, I will walk you right through it.

Calculate the capacity of your mould

Before you start calculating the capacity of your mould, keep in mind that in soap making every ingredient that you include in your recipe needs to be measured by weight.

Alright, so you have a few silicone moulds in front of you and want to know how much soap you need to make so nothing goes to waste. You can do as follows:

  1. Take one of your moulds and place it on your scale. Turn it on, select the weight option in grams and make sure you press the ‘tare’ option so the weight of the mould is not included.
  2. Pour water into the mould until you reach the top.
  3. Write down how much the water weights.
  4. Turn off the scale. That’s it.

The reason why using water is a reliable way to calculate the capacity of your mould is because 1 ml = 1 gram. I do like to use circular moulds so I found this method to be the easiest for me and it can be used for any shape.

The capacity of this mould is 100 grams.

yellow silicone mould

If you don’t have any of the equipment needed to make cold process soap bars yet, check our list of things you need to get started.

Calculate the amount of oils

Now we need to calculate the amount of oils needed. How do we do this?

As an example, I will be calculating the amount of oils that I need to fill 4 moulds with a capacity of 100 grams each. We have to do as follows:

Mould capacity (grams) x number of moulds = Total mould capacity (grams)
100 grams x 4 = 400 grams
Total mould capacity (grams) x 1,8 x 0,4 = Total amount of oils (grams)
400 grams x 0,70 = 280 grams
Based on this calculation, my recipe requires 280 grams of oils. When talking about oils, we are referring to liquid and solid oils, and butters.
Keep in mind that the multiplier could be a bit higher or lower depending on the density of the oils you are using, however, I use 0,70 as a general rule and I'm quite happy with the results so far.

Use a soap calculator

When coming up with a soap recipe, I like to use this soap calculator that tells me how much water, sodium hydroxide and essential oils I need for a perfectly balanced soap.
If you look at it for the first time, it might seem a bit daunting, but it doesn’t have to be. Here is what you need to select for a simple cold process soap bar:
  • Type of lye: NaOH⎪Sodium hydroxide.
  • Weight of oils: 280 grams⎪Based on the example I showed above.
  • Water as % of oils: 38⎪It can be left as it is, 38% of water is a good percentage for beginners.
  • Super fat: 5%⎪Super fat (or lye discount) is the amount of oils that are left unsaponified (not turned into soap), so a 5% super fat is a safe percentage and it’s highly recommended to leave it as it is.
  • Fragrance: 31 g/kg⎪This is completely optional. If you want to make an unscented soap bar, you can change it to 0. If using essential oils, the recommended percentage is 1-2% of the total amount of oils, so instead of 31 g/kg, you should change it to 10-20 g/kg.

The last piece of the soap calculator is to include in the ‘recipe oil list’ which oils and butters you want in your soap bar and the percentage of each of them. You press on ‘calculate recipe’ and… that’s all!

The only thing left to do is to view your recipe, gather all the ingredients, equipment and utensils and get ready for some soap making.

Scale photo by Tyler Nix on Unsplash.