# how to calculate a ratio?

Discussion in 'Beginners Soap Making Forum' started by Spice, Aug 6, 2017.

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1. Aug 6, 2017

### Spice

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Like 25% of water to oils or 38% lye concentration? Or any ratio:headbanging::headbanging:

2. Aug 7, 2017

### earlene

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Well, first, if you are using a lye calculator such as SoapCalc or Soapee, or any of the others I generally see online, the calculator does that for you. You only have to choose which you want in the appropriate box. If you don't make a selection in that box, the calculator chooses a default number.

If you are mixing something like a fragrance mixture to create your own fragrance, perhaps this will help understand Ratios:

1:3 = 1 part to 3 parts = a ratio of 1 to 3 (for a total of 4 parts)
So if you are mixing fragrances (Essential oils, for example) and you need a ratio of 1 part to 3 parts, what you end up with is 4 parts, where 1 part is the least amount of one EO and the other 3 parts are a different EO.

In terms of percentage the same 1:3 ratio becomes 25% of the first EO and 75% of the second EO = 100% of the total fragrance.

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3. Aug 7, 2017

### jbrewton

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25% of Water to Oil. In this case if you have 100g of oil you would use 25g of water.

Here is how it works: Cross Multiplication

25%/100% = Xg/100g

No multiply 25x100 = 2500

Now multiple 100 times X = 100X

So 2500 = 100X

Divide both sides by 100 and you get 25 = X

Hope that helps.

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4. Aug 7, 2017

### Spice

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interesting how i see that, so the one is a 25 of 100 ( like you said) and the other is three quarters=75.

This will help how I think when I am doing a blend.:bunny:

Like this too. I like to get different views, because I have a brain that see math as greek. Thanks

5. Dec 8, 2017

### iwannasoap

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For those who continue reading this...
I realize I am a day late and a dollar short but a ratio is the same as a division problem.
Meaning this "1:3" is the same as "1/3" this.
This means "1:3" The numerator part is INCLUDED in the 3 parts as a whole.
1/3 = 33.3% meaning the "1" is 33.3% part of the whole. The whole is the 3 parts or the denominator. One of those is 33.3%
Just like one quarter out of a dollar is 1/4.
You can also write it as a ratio of 1:4
1/4 = .25
Ratio's and division are exactly the same!
If you had a pizza with 10 pieces and you ate one then you ate 1/10 of the pizza OR it can be a 1:10 ratio.

6. Dec 9, 2017

### The Efficacious Gentleman

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Except that doesn't work at all, especially not for your dollar example at all -

1/4 is a quarter, the coin. Four of them in a dollar. The 4 of 1/4 means 4 parts, and the 1 means 1 of those 4 parts.

If you write that as 1:4, you now have 5 parts, not 4. You add the two parts together to get the whole. 1:1 means each side is 50%, not 100%, the whole is 2 and each side is 1.

So if 1/4 is a quarter and you write it as 1:4, there are now 5 quarter coins in total. Handy for getting some extra money, not so good for being useful maths.

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7. Dec 18, 2017

### Spice

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Thanks for clearing that up, how can I figure a 1:4 math? I see a lot of "just do a 3:2". So how can I, in my stupid little head, figure that out.

8. Dec 18, 2017

### The Efficacious Gentleman

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1:4 is a 5 part total, so think of it like 20 cents in the dollar.

Working with ratios depends on the direction in which you are working If you have your total amount and want to work out how that splits over the ratio:

Take your amount (let's say 175) and divide it by the sum of both sides of the ratio (1:4 becomes 1+4 =5). So one part of our ratio is 175/5=35. On one side we have 1 part and on the other 4, so we have to multiply that 35 by the numbers on both sides of the ratio. So 35*1 = 35. 35*4=140.

To check, add those two together and they make 175, which was our starting number.

When coming from the other direction, where you have a ratio and you know the amount for one side of it-

So I have a ratio of 1:4 and I know that the right side is 140. To work out the rest, I divide that 140 by 4 to get the base amount for each part of the ratio. 140/4 is 35. So we can now multiply that by the sum of the ratio parts (35*(1+4)) to find out the final amount, or multiply it by the left side of the ratio to find out how much that it.

I hope that didn't make it worse

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9. Jan 30, 2018

### jackznanakin

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I feel your pain. I've been sticking with MP for now because I see recipes for 30 this and 20 that and I'm over here just like, huh? 30% of what? How do I know what my total is to be figuring 30% of, but then I'm scared to ask it bc I know I sound stupid. And I sure don't want to hurt anyone if my math is off.

10. Jan 30, 2018

### earlene

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If it's an oil, it's the percent of oils. When you enter your recipe into your lye calculator (SoapCalc, Soapee, or whichever one you use), you can enter the percentage or you can enter the weight. If you use percentage, the calculator calculates the weight of each oil (when they all total up to 100%) based on the weight you choose for the total batch. So if I want to make soap with 1000 grams of oil, and I want it to be 30% OO and so and so forth, when I click on 'calculate' (or as with Soapee, since it works on-the-fly) the lye calculator tells me the weight I need for each oil.

If it's for FO's or for EDTA or for some other additive, you do need to know if it is supposed to be a percentage of oil or a percentage of the total batch size. Total batch size includes ALL ingredient weights, such as lye, water, FO, etc. There is a place on some of the lye calculators to indicate which you prefer for calculation in terms of percentage of other ingredients.

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11. Jan 30, 2018

### BrewerGeorge

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Don't over think it. Trust the calculators.

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12. Feb 2, 2018

### SaltedFig

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I could do with some maths! Thanks rnew2soap ...

The wages example:
Jim earns \$40k (an abbreviation for \$40,000.00)
Rob earns \$80k
The total earned by Jim and Rob is \$120k

The ratio between Jim and Rob describes how much they have each of the total.

So Rob earns two parts of the total they have earned, Jim earned one part of the total.
Which is a ration of 2:1, where each part is \$40k and the total is 3 x \$40k (or \$120k)

The gears example:
In the time that it takes Gear1 to turn two times, the slower Gear2 only does one turn.

So there was a total of 3 turns, with Gear1 turning twice and Gear2 turning once.

A 2:1 ratio.

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13. Feb 2, 2018

### earlene

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I beg to differ, renew2soap.

We are talking about soap here, not business economics. Regardless of what Lind, Marchal and Wathen say look at this:

Two parts water and One part NaOH. That is 2:1

You use twice as much water as you do NaOH. That is 3 total parts and equals a 33% Lye Concentation.

Measure 100 grams of NaOH. Measure twice that, or 200 grams of Water. Slowly pour and mix the 100 grams of NaOH into the 200 grams of water. You end up with a 33% Lye Concentration. It is a ratio of 2:1 or 1:2 depending on which item you put first, but all in all, there are a total of 3 parts, not just 2.

To take that further, how do you get a 50% Lye Concentration? With a 1:1 ratio, where 1 equal part is water and 1 equal part is lye. Two parts total in a 1:1 ratio of lye to water equals a 50% Lye Concentration.

Last edited by a moderator: Feb 2, 2018
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14. Feb 2, 2018

### SaltedFig

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Thanks Earlene, I did rather forget the important bit.

@rnew2soap your interpretation of how ratio's work is still wrong.

15. Feb 2, 2018

### cmzaha

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Dang...Thanks for reminding me I need to master batch a couple of gallons tonight

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16. Feb 2, 2018

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Yup!

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