Measurements vs. Percentages in Soap Making Recipes

How to Measure Soap Ingredients

Homemade soaps with ingredients

Betsie Van der Meer / Getty Images

While cooking a recipe for food usually allows some room for error, soap making is a completely different type of process. Precision is key in order for soap recipes to work, so every ingredient is weighed. This ensures that you're using the right amounts of each ingredient and that you're using the same measurement from batch to batch, recipe to recipe.

To allow soap makers to create soaps in different quantities, we often write recipes in percentages as well as measurements. Soap recipe ratios involve a little bit of math, but the benefit is that it allows you to easily adjust a recipe to fit any size mold. By using percentages for soap making measurements, you can also get a better feel for the qualifies of the soap you're making.

For example, let’s say you have a recipe that makes 2 pounds of soap. In it, you might have 1/2 cup of coconut oil. You try the recipe and the lather isn't as rich as you'd expect, so you'd like to increase the proportion of coconut oil. With measurements, this is hard; if you have percentages in addition to the measurements, it’s easy.

Converting a Recipe from Measurements to Percentages

We’ll start with a simple recipe to demonstrate how to convert a soap recipe into ratios. (Remember we're weighing everything, not using liquid measures.)

  • 12 ounces olive oil
  • 10 ounces palm oil
  • 9 ounces coconut oil
  • 8 ounces canola oil
  • 2.5 ounces castor oil
  • 2.5 ounces cocoa butter

This will make a 4 pound batch of soap. But what are the ratios of each oil? Is this a well-balanced recipe? And what if you want to make 7 pounds of soap?

Here’s how to make the conversion:

Add the ounces of oils together. In this case, it’s 44. Divide each individual weight by 44 to get the percentage of each oil in the recipe.

12 ounces olive oil divided by 44 = 27%
10 ounces palm oil divided by 44 = 23%
9 ounces coconut oil divided by 44 = 20%
8 ounces canola oil divided by 44 = 18%
2.5 ounces castor oil divided by 44 = 6%
2.5 ounces cocoa butter divided by 44 = 6%

Using these percentages, we can rewrite the recipe as follows:

27% olive oil
23% palm oil
20% coconut oil
18% canola oil
6% castor oil
6% cocoa butter

Let’s say you want to make a 7-pound (or 112-ounce) batch of soap. (Remember, that’s just the measurement of your oils. Leave room for the lye and water.) Multiply the percentage by the number of ounces of soap you want to make.

27% olive oil multiplied by 112 ounces = 30.2 ounces
23% palm oil multiplied by 112 ounces = 25.8 ounces
20% coconut oil multiplied by 112 ounces = 22.4 ounces
18% canola oil multiplied by 112 ounces = 20.2 ounces

Before you panic at the thought of doing all this math, or think you need to create an Excel spreadsheet to make soap, relax. Most online lye/soap recipe calculators scale your recipes easily and give you the recipe in both measurements and percentages.

Now, whether you’re creating a recipe from scratch or find one online, you can understand the proportions of the oils used and how to scale it to any size you like.