Lye Soap Calculator With Formulation Guide

Table Of Contents

The soap calculator is not intended to be a soap-making lesson. We have full tutorials and videos on the basics of making cold process solid soap and traditional liquid soap making on the blog. We also have a guide on how to use the calculator to formulate soap below

The Lye Calculator

Select your chosen oils, along with the weight or percentage. The lye soap calculator will then show the total weight of lye and water required. The result can be instantly adjusted by changing your preferred superfatting level or water/lye ratio, see below for the full calculator instructions and formulating soap guide

Soap Calculator Instructions

Start by naming your soap recipe.

  1. Choose either Solid or Liquid Soap (see how-to guides below).
  2. Choose your Preferred Units Of Measure, Grams or Ounces (I highly recommend Grams for more accuracy). There is a third option which is to select your oils as a percentage of 100. If you do select the Percentage option, you must input your Total Ingredients Weight in the field that opens up to the right.
  3. Select each of your ingredients along with their individual weight. OR, if you chose to use percentage in the previous step, you input a percentage for each ingredient, making sure the total ingredients add up to 100%. The Total Ingredients Weight is calculated and shown below.
  4. Once you have entered all of of your ingredients (along with their weights or %), move on to view the recipe results and superfat/water ratio options.
  5. I always recommend to superfat at 5% as standard, so the default is set to 5%. However, you can increase this up to 10% or decrease it to 0% (see guides below). 
  6. I usually recommend selecting a Water Ratio of 2/1, that’s a pretty good standard for any hard soap. For liquid soap, you would want 3/1 (see how-to guides below).
  7. Double-check that all of your ingredients, weights, and recipe options have been set correctly before using the, Total Lye Required and Total Water Required values.
  8. Use the Send To Email button to get the recipe sent to you by email (no spam privacy policy).

Important Notes

  • Please do not rely solely on its output to create your soap. Take all necessary precautions when working with Lye and always test your soap with a PH strip before use. Learn how to make cold process soap here, or how to make liquid soap here.
  • The lye calculator assumes a 97% purity for NaOH (Sodium Hydroxide) and a 90% purity for KOH (Potassium Hydroxide), these are most commonly sold by most suppliers.
  • The sap values you see in the calculator, are taken as an average of saponification values provided by Certified Lye and many other trusted sources. But please remember that depending on a variety of factors, saponification values of oils can change.
  • Please send me any feedback you have for the calculator, including any bugs or errors, using the comments below or the contact form here Going forward this will help me improve and perfect the app for everyone. I’m open to developing it further if people can see possible additions or improvements.

Soap Making Guides

Working quickly but carefully so not to let the batter harden in the bowl, pour or spoon your batter into your soap mold

If you’re a complete beginner or you haven’t made cold process, hot process or liquid soaps before, I strongly recommend you follow a tutorial/pre-formulated recipe before formulating your own soap recipe using this lye calculator.

my best bastile soap recipe
Angela Wills
How To Make Castile Soap At Home

Here’s how to make Castile soap, it’s absolutely one of my favorites. It’s simultaneously one of the most inexpensive soap recipes you can make (making it a great beginner soap), but also the most gentle of cleansers at the same time.

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Homemade liquid soap
Angela Wills
Traditional Lye-Based Natural Liquid Soap Making

After a few weeks testing and perfecting the process of liquid soap making, I’m now the proud owner of several colorful bottles of lush smelling totally natural loveliness. No surfactants here to irritate my skin, just nourishing creamy soap packed full of moisturizing oils.

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Formulating Your Soaps

soapmaking for beginners

If you’ve come to the Savvy Homemade soap calculator and haven’t used it before, you may be wondering what all the fuss is about. Perhaps you’ve followed a few of my tutorials, or others across the web.

But have you ever asked yourself, can I come up with my own soap recipe? The answer is, absolutely! And this guide will talk about some of the more important aspects of choosing a recipe using the lye calculator.

Oils, Butter & Waxes, Oh My!

Besides the water and lye, your recipe will be comprised mostly of carrier oilsbutters and occasionally some waxes.

While there are other ingredients we will talk about later, these are the bulk of your recipe and it’s important to get them right!

When you’re choosing oils, butters and waxes for your soap, you have a lot of freedom. Liquid oil is the only thing that you absolutely need. In fact, you can make soap with just olive oil! The butters and waxes are optional but definitely worth considering as they can add some wonderful properties to your soaps.

fats and oils used in cold process

As a basic ratio, I like to recommend 50% liquid oil, 25% solid oil (something like coconut) and 25% cosmetic butter. This should give you a lovely soap that is medium-soft and rich with nourishing qualities. If you want to use a wax, exchange it with 5% of the butter (so 50% liquid oil, 25% solid oil, 20% cosmetic butter and 5% wax). Keep in mind that all butters and wax have different densities, so this basic formula may have to change depending on the type you use.

For instance, if you want to use a wax like beeswax in your soap but you’re vegan, you can exchange it for candelilla wax. However, candelilla wax has double to the stiffness of beeswax, and so you may want to use 2.5% instead of 5% in order to achieve a similar texture to your soap. There’s a similar story for shea butter and cocoa butter, cocoa is harder and will change the texture when substituted (although both are 100% vegan in this case).

Nevertheless, these ratios can totally be stretched, played and experimented with using the lye calculator. You could end up with a new breakthrough formula in soap making, or perhaps your next flop. Keep in mind that cosmetic butters and waxes (waxes especially) can speed up trace considerably. If using high butter or wax ratios, consider using oils that don’t trace very quickly to slow down the chemical reaction.

Soap making is all about experimenting

Sometimes you will formulate a soap and it just doesn’t turn out the way you were hoping. Try to remember that this isn’t necessarily a bad thing. When you make a mistake or things go wrong, you’re learning valuable lessons about what will and won’t work.

Just start off simple, using readily available and affordable oils, butters and waxes and always use the calculator in order to figure out how much water and lye to use. That way, it really shouldn’t matter if things don’t necessarily go to plan. Even the very best soap makers make mistakes sometimes, just keep yourself motivated and you’ll be a master in no time!

Fatty Acids, What Are They Good For, Cleansing, Conditioning, Lather?

All carrier oils, butters and waxes have what we call ‘fatty acids‘. Without going into too much unnecessary detail, these substances are what lend wonderful and useful properties to our soaps! Let’s take a look at a breakdown of the most commonly found fatty acids in our soap making ingredients and how they affect our soap.

Fatty Acid Cleansing Conditioning Fluffy Lather Creamy Lather
Lauric acid Yes Yes   Yes
Linoleic acid Yes      
Linolenic acid Yes      
Myristic acid Yes Yes   Yes
Oleic acid Yes      
Palmitic acid     Yes Yes
Ricinoleic acid Yes Yes Yes  
Stearic acid     Yes Yes

Each oil, butter or wax contains differing amounts of these fatty acids. Many contain a few of them, but not all of them.

Considering the fatty acid breakdown of each individual soap making ingredient is an important aspect of formulating a soap. Nevertheless, individual oils, butters and waxes can bring further benefits, and so try not to focus solely on fatty acids.

Most Commonly Used Oils, Fats & Butters With Properties & Sap Values

Let’s take a look at a breakdown of the most commonly used oils, butters and waxes for soap making, including their individual benefits, fatty acid content and any specific considerations and information regarding ratios (if applicable).

If you’re using our lye calculator, you don’t need to worry too much about the SAP values as the calculator will handle that. However, I have listed them for educational purposes.

Oil, Butter or Wax Properties & Benefits Fatty Acid Content SAP Value
Almond oil A wonderful, all-round oil. A great addition to pretty much any type of soap. High in Oleic acid, with low levels of Linoleic, Palmitic and Stearic acids. 0.1367
Argan oil A beautiful oil with powerful conditioning benefits. Best used in superfatting due to its high cost. High in Linoleic and Oleic acid, low levels of Palmitic and Stearic acids. 0.1361
Avocado oil Great oil for anyone with sensitive skin. It’s super moisturizing due to it containing compounds that do not saponify. High in Oleic acid, low levels of Linoleic, Myristic, Palmitic and Stearic acids. 0.1337
Beeswax Should be used at around 5% in soap formulas. N/A 0.0689
Castor oil Lends a quick foaming and rich texture to soap fomulas, as well as a great moisturiser for soap. High in Ricinoleic acid, low levels of Oleic, Palmitic and Stearic acids. 0.1286
Cherry Kernel oil Fantastic in conditioning bars, but should be used with other oils and butters to produce a harder soap. On its own, your bars will be a little on the soft side. High in Linoleic and Oleic acids, low levels of Palmitic and Stearic acids. 0.1350
Cocoa butter A lovely cosmetic butter that adds great cleansing benefits, as well as producing a very stable soap with fluffy, creamy foam. High in Oleic, Palmitic and Stearic acids, low levels of Linoleic acid. 0.1378
Coconut oil A wonderful solid oil that I usually always recommend using in any soap. Wonderfully, moisturising, although actually becomes drying in quantities over 35% due to its high Lauric acid conteNT. High in Lauric and Myristic acids, low levels of Linoleic, Oleic, Palmitic and Stearic acids. 0.1780
Cranberry seed oil Perhaps not a great oil to use on its own, this oil is great when used with oils that deteriorate soap quickly, due to its unique structure and resistance to oxidization. Low levels of Linoleic, Oleic, Palmitic and Stearic acids. .1350
Grapeseed oil Great oil for conditioning and softening the skin, although it can produce a soap that is a little too soft so blend with other oils and cosmetic butter. High levels of Linoleic acid, low levels of Oleic, Palmitic and Stearic acids. 0.1321
Hazelnut oil A great oil to add cleansing benefits to your soap, although does take much longer to reach trace. Perhaps a good oil to use in conjunction with ingredients that trace very quickly in order to produce a slower-moving soap. High levels of Oleic acid, low levels of Linoleic, Palmitic and Stearic acids. 0.1359
Jojoba oil Not actually an oil, but rather a liquid wax! Nevertheless, produces a rich bar with a dense lather, but isn’t all that moisturizing in soap on its own. I recommend blending with other oils, or superfatting it. High levels of Stearic acid, low levels of Linoleic, Myristic, Oleic and Palmitic acids. 0.0695
Lard A cheap, easy to get hold of soap ingredient that lends lovely cleansing properties to your soap. However, it is not suitable for vegetarians or vegans. High levels of Oleic and Palmitic acids, low levels of Linoleic, Myristic and Stearic acids. 0.1399
Mango butter Adds wonderful conditioning and moisturizing benefits to your soap, but does harden it considerably. Great to use with oils that produce a very soft soap, but otherwise should not be used in quantities over 15%. High levels of Oleic and Stearic acids, low levels of Linoleic and Palmitic acids. .1360
Olive oil Virgin is fine to use, but I strongly recommend using pomace oil as its much cheaper. Makes a wonderful conditioning bar. Olive oil soaps are very mild, so great for use on babies and young children. High levels of Oleic acid, low levels of Linoleic, Linolenic, Palmitic and Stearic acids. 0.1353
Palm oil Probably one of the best oils to use in terms of how it behaves in soap. Nevertheless, it is a very controversial ingredient due to sustainability and how harvesting affects local wildlife. For these reasons, I do not recommend this oil to any soap maker, you can substitute with babassu oil, tallow or lard. High levels of Oleic and Palmitic acids, low levels of Linoleic, Myristic and Stearic acids. 0.1440
Peach Kernel oil Great for sensitive skin, produces a lovely milk soap with a creamy lather High in Oleic acid, low levels of Linoleic, Linolenic, Palmitic and Stearic acids 0.1361
Rice Bran oil Produces a great conditioning soap and will make skin feel soft and well hydrated. However, its lather is somewhat poor. Best blended with other oils. High in Linoleic and Oleic acids, low levels of Palmitic and Stearic acids. 0.1290
Rosehip Oil An oil known for it’s powerful healing properties. Nevertheless, these properties are kind of lost when used in the bulk of your soap batter. Best used for superfatting. High in Linoleic and Linolenic acids, low levels of Oleic, Palmitic and Stearic acids. .1350
Safflower oil This takes a long time to trace, as well as deteriorates soap quite quickly. Best used with other oils to prolong life as well as speed up trace. High levels of Linoleic and Oleic acids, low levels of Palmitic and Stearic acids. 0.1374
Shea butter This butter is super moisturizing and will nourish your skin. In soap, it produces a soap that is super creamy and ultra-moisturizing due to its content of un-saponifiable’s High ion Oleic and Stearic acid, low levels of Linoleic and Palmitic acids. 0.1296
Sunflower oil This oil can deteriorate very quickly in soap, and so best used with long-lasting oils with high vitamin e content. High in Linoleic acid, low levels of Linolenic, Oleic, Palmitic and Stearic acids. 0.1358
Wheatgerm oil Rich in antixidants and vitamin e, a great oil to use in conjunction with any oils that have shorter shelf lives. High in Linoleic acid, low levels of Oleic, Palmitic and Stearic acids. 0.1319

Superfatting With the Lye Calculator

So here’s the deal with superfatting. When you make soap at home, the majority of the oils saponify (turn to soap). However, superfatting allows you to add extra oil that won’t saponify, leaving you with a soap that has luxurious oils left over to nourish your skin.


I always recommend to superfat at 5% as standard, so when you use the Savvyhomemade lye calculator for soap making you will see that the default is set to 5%. However, you can increase this up to 10% or decrease it to 0% by using the superfatting level slider. For a super luxurious soap, you may wish to have a relatively high superfat content. However, a teenager with acne wouldn’t benefit from superfatting over 3%. So when deciding how much to superfat, always keep the purpose of the soap at the forefront of your mind.

If you want to superfat with the bulk oils of your recipe, my soap making calculator will handle that for you when you use the superfatting slider. This is great, because it is easy to do and quite effective. Nevertheless, you will not be able to guarantee which oils in your recipe will be superfatted, or your superfatting will be split across your oils equally.

Making Use Of Precious Oils When Superfatting

However, there are times when you might want to make use of precious oils for superfatting, which may require you to be more precise. Argan oil is an excellent example of this. Because argan is so damn expensive, using it in the bulk of your soap will make it extremely expensive to reproduce. This is especially problematic for anyone who plans to sell their soap.

While you can add argan oil to the calculator, you will have the problem of all of your oils being superfatted as opposed to just your argan oil. If you want it more precise, we’ll need to use a little math. Don’t worry, it’s nothing you can’t do on a calculator.

So, if you want to superfat with something like argan oil, use the calculator as you normally would, but leave out the argan and make sure the lye calculators superfatting slider is set at 0%. Then, you are free to add up to 10% of your argan oil by adding it at trace with your aromas, colors and added botanicals. Though I would recommend 5%.

The Formula

If you’re not sure how much 5% of your total batch is, there’s a simple formula you can follow. Take the total weight of your soap batch, divide that by 100 and then times that number by 5 (or whatever percentage you wish to superfat). That should give you the amount of argan oil you’d need to use.

So, for example, if my batch is 1.3kg and I wanted to superfat with argan oil at 5%, I would follow this calculation: 1300/100*5 = 65g. I would then add 65g of argan oil at trace, along with my extra ingredients. While some of this may still saponify, it is much more likely to remain as a superfat when you add it at trace, as opposed to with the bulk of your oils in the emulsion stage.

Saponification Values

The sap values you see in the chart above, of which are the same used by the calculator, are taken as an average of saponification values provided by Certified Lye and many other trusted sources. But please remember that depending on a variety of factors, saponification values of oils can change.

For example, sap values may change depending on the supplier, manufacturer, region of origin and even time of year. However, this should not affect you when using this calculator, as the differences will only be small and margin for error is minimal.

If you would like to check the sap value we have applied to a specific oil, select it and set the weight to 1. As an example, if we choose almond oil and set the weight to 1 gram, it will show the sap value is 0.137

Water/Lye Ratios With the Soap Making Calculator

The amount of lye and water you’ll need to properly saponify your oils, butters and waxes into soap will be handled by the calculator. So, no need to get your calculator out for this one!

adding water to lye when making castile soap

I usually recommend selecting a ratio of 2/1 in the water/lye section of the calculator. That’s a pretty good standard for any hard soap. For liquid soap, you would want 3/1.

You’ll notice I have offered the option to lower the ratio in the calculator. This is there for experienced soap makers who want to try and speed up saponification.

Sometimes certain soaps can take a very long time to harden in the mold (e.g. when making castile soap I use 1.5/1). By lowering the amount of water, you can get that soap out and start curing it earlier. Nevertheless, this does leave more room for error. I would only recommend utilizing this option if you’re experienced with making soap.

Other Ingredients Worth Thinking About

Before considering adding any extra ingredients, keep in mind that all of the below will accelerate trace, some quicker than others. Just be sure to add these at a light trace, right before you plan to pour into the mold.

Essential and Fragrance Oils

We all want a nice smelling soap, this is where essential and fragrance oils come in! Let’s talk about them separately, though, because both have their strengths and weaknesses.

add your essential oils

Essential oils

are amazing in soaps. They smell wonderful but also have many benefits that can be imbued in your soaps. They’re also 100% natural, and so great for anyone who wants to avoid synthetic chemicals. To learn more about these benefits and where to buy them, take a look at our essential oil use guides.

However, essential oils can hurt your wallet. Because they’re a natural product, supply is not always assured. This, in conjunction with the process in which they’re extracted, they can be very expensive and their price can vary from year to year.

Furthermore, various factors (such as climate) can change how essential oils smell. For instance, if the region that grows the lavender used for your essential oil has less rainfall one year, this could impact the quality of the essential oil. So there are a variety of issues regarding essential oils that you should keep in mind, especially when it comes to producing a consistent product.

Fragrance oils

Now, let’s chat about fragrance oil. These aromatic, albeit synthetic oils are the unnatural cousins of the essential oil. They’re cheaper, more consistent and the supply is always available. They also come in waaaaaay more varieties than essential oils do. Want a soap that smells like blueberry muffins? Fragrance oils are the way to go.

But, there’s a big catch. Because they’re synthetic, they have literally no benefit other than that they smell nice. They’re also packed full of artificially produced chemicals made in laboratories. I don’t know about you, but I don’t like the idea of smearing my body with something so unnatural. While the long term research on the safety of fragrance oils doesn’t currently exist, I just personally wouldn’t chance it.

There’s also something worth mentioning, and that’s how fragrance oils behave in soap. I find fragrance oils to be the bane of my soapmaking life. I can’t tell you the number of times I’ve had soap rice after adding them at trace. While you can buy fragrance oils that are formulated for cp and hp soap making, even those seem to be a bit hit and miss sometimes. Fragrance oils are great for melt and pour soap, but just don’t seem to be great for cp and hp soap.


Dying your soaps can be a great way to make them more beautiful and eye-catching. Like essential oils and fragrance oils, you have two options here; natural and unnatural.

adding lavender color in hot process

For the natural, there are a few options you can go for. Tarragon, for instance, is a great way to get a nice orange looking soap without impacting the scent profile of your soaps. There are other options, though, so take a look at my soap colorant section of my soap supplies page. The only problem is that you are more limited in what you can do and what colors you can get out of natural dyes. They’re also not all that vibrant, either.

As for unnatural, you have the micas. While mica is technically a naturally occurring mineral, many of the micas you find on the market are adulterated with synthetic pigments to get them to look nice and bright. While you’ll see many suppliers claiming their micas to be all-natural, I’m not sure I always trust them on that one.

Nevertheless, I have used micas many many times and haven’t have a problem. They are beautifully bright, vivid and come in a plenitude of colors, shades and hues. I tend not to use a lot of mica in my soaps anyway, so I think a pinch of something not so natural probably won’t hurt. Whereas dumping a load of synthetic fragrance oil is, for me, a big no-no.

Be careful when using anything that claims to be a liquid soap dye in your cp and hp soap. These are usually formulated for melt and pour soaps and not for cp or hp methods. Always make sure the product say it is suitable for cp and hp, otherwise pass on it.

Added Extras

Now for the little extras that aren’t necessary, but could make your product that bit more interesting or useful.

adding dried mint to soap

First, let’s talk about added botanicals. Often I’ll add dried or crushed organic herbs into my soap. A good example of that is my lavender and mint recipe, where I use crushed dried mint leaves. These add a great ascetic to your product and also scream ‘I am natural’ to your customers (if you sell your soaps, that is).

Be careful what you choose, though. dried flowers, for instance, are great when sprinkled on top but completely lose their color when stirred into the batter. Just be mindful and do your research.

Other added extras include exfoliants. Adding something like poppy seeds, jojoba beads or crushed almond shells can give your product an added exfoliating benefit. You’ll be able to clean your skin but also get rid of dead skin cells at the same time! I love doing this, and the pieces of exfoliants can look great in your soaps, too!

Functional Additives

Lastly, we have functional additives. Sometimes you’ll want to add an extra ingredient that does something specific. Lactic acid, for instance, jumps to mind immediately. This ingredient will make your soap harden up much more quickly. Its something I have worked with in the past, but I personally prefer to formulate a recipe that works great on its own.

Another optional ingredient you could try is titanium dioxide. This product will help lighten your soap. An all-natural soap has a tendency to look a little beige or dull. By adding this, you can actually get a soap that looks very white and pure. Nevertheless, it is entirely unnatural and I ordinarily will not make use of it.

adding titanium dioxide

This list of functional ingredients to use in my soap calculator will likely get longer as I discover new ones, so come back from time to time and check out what I’ve discovered!

All Homemade Soap Recipes

Angela Wills

Your Help

Please send me any feedback you have for the calculator, including any bugs or errors, using the comments below or the contact form here Going forward this will help me improve and perfect the app for everyone. I’m open to developing it further if people can see possible additions or improvements.

Thanks, Angela

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