Calculating and Using Percentages to Formulate

AuswertungenUnderstanding how percentages work when calculating a recipe is very important.  It’s one of the biggest questions I get asked from new soap makers.  How important is it?  The HSCG has questions on their certification exam on this topic!  That should tell you just how important it is.

It’s a question I’ve answered enough times that I figured it was worth taking the time to write a blog post about it.  This way I can refer questions back to it and potentially help those who don’t know who to ask for help.

I’m sure you’ve seen recipes that look like this:

20% Coconut Oil
20% Palm Oil
50% Olive Oil
10% Shea Butter

What does this mean though if you want to convert the percentages into ounces so you can make soap?  First step is to convert  the percentage into a decimal.

So you take the percentage and divide it by the total percentage of all items.

In this case: 20 + 50 + 20 + 10 = 100

20 / 100 = .20
50 / 100 = .50
20/ 100 = .20
10/ 100 = .10

Once you’ve converted the percentages you can then determine the amount of oil you’ll need. You simply take the weight of the batch and multiply it by the converted percentage.

With that in mind let’s go back to the problem on hand.  Let’s say we have a total weight of oils of 28oz.  We take that and multiply it by each percentage.

.50 x 28 = 14.0
.20 x 28 = 5.6
.20 x 28 = 5.6
.10 x 28 = 2.8

If we did our math right then 14 + 5.6 + 5.6 + 2.8 should add up to 28.  Woohoo! We did our math right.  Now you can take the ounces and plug them into a soap calculator to calculate the amount of water/lye you’ll need.

Part 2

Now if you understand this then you can calculate recipes even if you just know the weight of one of the oils! So we know that olive oil makes up 14oz of the recipe and we know that olive oil is 50% of the recipe. Before you can proceed you have to determine the total weight of oils this recipe will make.

If olive oil is 50% then we need to account for another 50% in oils. Simple math tells us that if half is 14oz then just add another 14oz (or double 14) to it and the total weight if the recipe is 28oz.  Now that we know this we can apply the same method as above:

.20 x 28 = 5.6
.20 x 28 = 5.6
.10 x 28 = 2.8

Part 3

Okay, now that you understand that I’m going to make it harder!  What if it’s not “simple math” and you can’t go oh I know 50% is half?  Then just set up your problem as an algebraic equation: Let’s look at a NEW recipe.

An oil blend is to contain 50% olive, 20% palm, and 30% coconut.  How many pounds of olive oil should be used with 8 pounds of coconut oil?

What your recipe has: (converted to decimal)
50% olive oil (.50)
20% palm oil (.20)
30% coconut oil (.30)

What we KNOW for actual weights of oils:

50% olive oil = ?
20% palm oil = ?
30% coconut oil = 8lb

Let’s set it up as an algebraic formula:
You need to determine: 8lb is 30% of what (x)?

So, 30% = .30

8lb = .3x (x represents the total weight of the batch)

Then just solve the formula: (to get “x” on its own you have to divide each side by .3)

8/.3 = .3x / .3

(the .3 cancels out leaving you with just “x”)

x = 8/.3

x = 26.6

Now that you know the TOTAL weight of the recipe you can calculate 50% olive oil.

50% x 26.6

(convert the 50%)
.5 x 26.6 = 13.3lb

If you’re studying to take the Certification Test you’ll see questions like this:

An oil blend is to contain 50% olive, 20% palm, 20% coconut, and 10% Shea Butter.  How many pounds of palm oil should be used with 6 pounds of Shea butter?

You can answer this question by doing the above math.  Figure out the TOTAL WEIGHT OF THE OILS in that recipe.  Then once you know that you can CALCULATE the percentage of whatever oil they’re asking for!

Learn to understand percentages! It’s really important and will be an invaluable skill for you in your soap making career.  I offer an advance class on Formulating a Recipe that goes over percentages.  If you’re local to Massachusetts and are interested in it watch my calendar page (www.jennifersoap.com) I offer the class once or twice a year.

So, give it a shot?  What’s the answer to the above question?  how many pounds of palm oil should be used?

Side Note

Most molds hold either 2lb, 2.5lb, 3lb, 5lb or 10lb of oils.  Part of the total weight of a batch will be made up of the lye/water solution.  So, a 2.5lb batch of soap doesn’t have 40oz of oils total.  Only a percentage of that will be oils. The rest will be your lye/water.  To help you get started with your own recipe calculations I’ve calculated the amount of oils needed for each mold weight and am sharing it with you.  Here’s a little “cheat sheet”:

Oil Cheat Sheet
2.5lb Batch  = 28oz oil
3lb Batch    = 34oz oil
5lb Batch    = 55oz oil
10lb Batch   = 110oz oil

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4 Responses to Calculating and Using Percentages to Formulate

  1. I got 5.32 lb. on the Palm oil above. Is that right? The weights are only off by .02 oz. total weight for the batch.

    • Jennifer says:

      An oil blend is to contain 50% olive, 20% palm, 20% coconut, and 10% Shea Butter. How many pounds of palm oil should be used with 6 pounds of Shea butter?

      50% Olive = ?
      20% Palm = ?
      20% Coconut = ?
      10% Shea Butter = 6lb

      Let’s set it up as an algebraic formula:
      You need to determine: 6lb is 10% of what (x)?

      6lb = .1x

      6/.1 = x
      x = 60

      So our total weight of oils for this batch is 60lbs (This is going to be a massive batch of soap ha!)

      Now that you know the TOTAL weight of the recipe you can calculate 20% palm oil.

      So Palm Oil makes up 20% of the batch we take:
      20% x 60
      .2 x 60 = 12lbs

      So the answer is 12lb

  2. Sorry! I was originally working on the problem in Part 3, and was trying to figure out the amount of Palm Oil in that problem! It had a question mark and no answer, so I thought I’d try to solve that! I’m sorry about the confusion in the numbers!

    I did the math on this current problem, and did, in fact, come up with 12 lbs.! GOT IT!

    Thank you SO MUCH for the tutorial. I’m really relieved to be able to try to figure this out now!

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