How to Use a Lye Calculator

Learning to use a soap calculator might seem confusing, but in today’s blog post I’m going to take out all the mystery by sharing how to use the Soap Calculator on .

Knowing how to use a soap calculator is important because:

1. You should always enter recipes you find online into a soap calculator to make sure they are correct.

2. It can help you if you want to create your own recipe.

3. It can help you if you find a recipe written in percentages and you want to know how much it is in weight.


So let’s get started:

  1. First go to the website:  and click on “Recipe Calculator” at the top.



2. You’re going to reach this page. There’s going to seem like there’s a lot of information and ads, but I want you to focus on the part in the middle



3. Now let’s bring our attention to the top section:


And we will start where it is numbered

  1. Type of Lye
  2. Weight of Oils
  3. Water
  4. Super fat


In number 1 Type of Lye, you will keep it at NaOH because we are making Hard Bar Soap. KOH is for making Liquid Soap.  They are 2 different types of Lye, so we will be using NaOH.

In number 2: Weight of Oils: you will decide if you want your oils to be weighed in Pounds, Ounces, or Grams. (Grams is always more accurate). In the little green rectangle you will enter the total amount of soap you are making depending on the size of your mold. So if you know your mold holds 5 pounds of soap, you will enter 5 lbs.

In number 3: you will decide if you will have a water discount (this is a more advanced technique), or you can leave it at 38 which is what we will do.

In number 4: you will decide how much you want to super fat your batch.  Super fat means you want to keep some oils unsaponified in your soap.  It’s always better to have more oil than more lye. Choose a value between 1-5. I will keep it at 5. In the fragrance, I will make it 0 because I like to calculate how much fragrance I need separately. Because different fragrances have different ratios.


So based on the above explanation, my new entries will look like this:




4. Now let’s move on to next section of the page where it says 5, and 6. Don’t worry about section 5. In section 6 we will enter our oils:




I have the following recipe in percentages that I will enter:

Coconut oil %30

Olive Oil %30

Almond Oil %20

Castor oil %10

Shea Butter %10


5. To add each oil, You need to

  1. Scroll and find the oil that you are looking for.
  2. Click on the oil
  3. Then click the little red + sign in section 6 



6. n the image below I’ve added all of my oils in the same way. Be sure to click the plus sign next to the row where you want to add the next ingredients, or you will just replace the oil you added before. 


7. Next, I’m going to enter the percentages next to each oil, based on the recipe that I have.


8. Next, Click on Calculate Recipe


9. Now you can notice that the values have change all over the page.

I want to bring your attention to the orange rectangles. Notice how the percentages should always equal 100. The 5 in the pounds is based on the 5 pounds we entered in the beginning in Section 2.

Next, click on “View or Print Recipe” . A new window will open to see the full recipe with more details



10. Here is the new window with the  full recipe 


11. Now I want you to bring your attention to this section in red. This shows you the exact weight of the oils that you need to make 5 pounds of soap, in both ounces and grams


12. This next Section Shows you how much Water and NaOH you need:


13. The bottom part of the page, shows you the qualities of the soap you’re going to make:


Let’s take a look at the the Green section for a minute.

The First column describes different qualities a soap bar has.

The second column gives a recommended range for each quality

The Third column tells you where your recipe stands.


So you can see as an example that the recommended hardness of a soap bar should be between 29-54. And our recipe is at 35, so it is at mid range.


Cleansing is recommended to be be between 12-22, and our soap is at 20, so it’s at the high range.


If you want to change any of these qualities of your soap, you can go back to your recipe and change the percentage of each oil in your recipe.


14. You can now print this recipe out and write down any comments you have, or additives you would like to add to your soap. 

I highly recommend that you still print out a copy of your own formulation work sheet and write down the actual process you go through every time you make your recipe.


I hope you found this article helpful,



1 comment

  • Helpful but Can I see different recipe run in grams please


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