Explaining SAP values in soapmaking
Soap Science Series
SAP Values: The Complete Australian Guide to Saponification
What every Australian soapmaker needs to understand about saponification values, lye calculations, superfat, and why getting the maths right is non-negotiable for a safe batch.
Always verify with the Soapmaid Lye Calculator
Before your first batch of cold process soap, before you choose your fragrance oil, before you even think about design — you need to understand one number: the saponification value of your oils. Get it right and you have a safe, beautiful bar. Get it wrong and you have a caustic mess. This guide demystifies SAP values completely, from the chemistry to the reference table you'll use every time you soap.
What Is Saponification?
Saponification is the chemical reaction that turns oils and fats into soap. When an oil — a triglyceride of three fatty acid chains bonded to a glycerol backbone — reacts with a strong alkali (sodium hydroxide for bar soap, potassium hydroxide for liquid soap), the fatty acid chains are cleaved from the glycerol. The sodium or potassium binds to those fatty acids to form soap salts, while the glycerol is released as glycerine — a natural by-product of cold process soap making that remains in handmade bars as a skin-conditioning agent.
The word "saponification" comes from the Latin sapo, meaning soap. The reaction is exothermic — it produces heat — which is why your soap batter warms up in the mould during the first hours after pouring.
The saponification reaction in plain language:
Triglyceride (oil/fat) + NaOH (lye) → Sodium soap salts + Glycerine
The specific soap salt formed depends on the fatty acid and the alkali used. Olive oil saponified with NaOH produces sodium olivate. Coconut oil saponified with NaOH produces sodium laurate, sodium cocoate, and related salts. These are the INCI names you list on your cosmetic labels — not the original oil names.
What Is a SAP Value?
A saponification value (SAP value) is simply the amount of lye required to fully saponify one gram of a specific oil or fat. It is expressed as grams of lye per gram of oil. Every oil has a unique SAP value because every oil has a unique fatty acid composition — and different fatty acids require different amounts of lye to react completely.
| Lye Type | Chemical Name | Use Case | Typical SAP Range |
|---|---|---|---|
| NaOH | Sodium hydroxide (caustic soda) | Hard bar soap | 0.069–0.190 g/g |
| KOH | Potassium hydroxide | Liquid or soft soap paste | 0.097–0.257 g/g |
"The SAP value is the single most important number in soap making. Every batch begins with it — and ignoring it is the most dangerous mistake a new soapmaker can make."
Why KOH SAP Values Are Higher Than NaOH
KOH SAP values are approximately 1.40 times higher than NaOH values for the same oil. Potassium hydroxide has a higher molecular weight (56.1 g/mol) than sodium hydroxide (40.0 g/mol) — more grams of KOH are needed to provide the same number of hydroxide ions. Commercially available KOH is also typically only 90% pure, meaning you must divide your theoretical KOH amount by 0.9. The Soapmaid Lye Calculator handles this automatically.
Why Every Oil Has a Different SAP Value
SAP values vary because different oils contain different fatty acids with different molecular weights and chain lengths. The rule is: shorter fatty acid chains have higher SAP values (more moles of fatty acid per gram = more lye needed), while longer chains have lower SAP values.
| Fatty Acid | Chain | Found In | SAP Contribution |
|---|---|---|---|
| Caprylic (C8) | Short | Coconut, palm kernel | Very high |
| Lauric (C12) | Medium-short | Coconut oil (45–52%) | High |
| Myristic (C14) | Medium | Coconut, palm kernel | High |
| Palmitic (C16) | Medium-long | Palm oil, lard, shea | Medium |
| Stearic (C18:0) | Long | Shea butter, tallow | Medium |
| Oleic (C18:1) | Long | Olive, high oleic sunflower | Medium-low |
| Ricinoleic (C18:1-OH) | Long + hydroxyl | Castor oil (85–92%) | Low (unique structure) |
| Linoleic (C18:2) | Long polyunsaturated | Sunflower, grapeseed | Low |
SAP Value Reference Table: 40+ Common Oils
This table covers the most commonly used soap-making oils in Australia. Values are averages — actual values can vary slightly between batches and suppliers. Always use the Soapmaid Lye Calculator for your final lye amounts.
| Oil / Fat | NaOH SAP | KOH SAP | Primary Fatty Acid |
|---|---|---|---|
| Tropical & High-Lauric Oils | |||
| Coconut Oil (RBD or Virgin) | 0.190 | 0.257 | Lauric (45–52%) |
| Palm Kernel Oil | 0.183 | 0.247 | Lauric (48–52%) |
| Babassu Oil | 0.175 | 0.237 | Lauric (44%) |
| Murumuru Butter | 0.175 | 0.237 | Lauric (46%) |
| Oleic-Dominant Oils | |||
| Olive Oil (Extra Virgin / Pomace) | 0.134 | 0.190 | Oleic (55–83%) |
| High Oleic Sunflower Oil | 0.136 | 0.192 | Oleic (70–80%) |
| Avocado Oil | 0.133 | 0.187 | Oleic (55–70%) |
| Sweet Almond Oil | 0.136 | 0.192 | Oleic (62–86%) |
| Apricot Kernel Oil | 0.135 | 0.190 | Oleic (58–74%) |
| Argan Oil | 0.136 | 0.191 | Oleic (43–49%) |
| Macadamia Oil | 0.139 | 0.194 | Oleic (55–67%) |
| Camellia (Tea Seed) Oil | 0.137 | 0.193 | Oleic (74–87%) |
| Hazelnut Oil | 0.136 | 0.192 | Oleic (66–83%) |
| Marula Oil | 0.135 | 0.190 | Oleic (70–78%) |
| Linoleic-Rich Oils | |||
| Sunflower Oil (Regular / High Linoleic) | 0.134 | 0.190 | Linoleic (50–70%) |
| Grapeseed Oil | 0.126 | 0.179 | Linoleic (58–78%) |
| Hemp Seed Oil | 0.135 | 0.193 | Linoleic (50–60%) |
| Rosehip Oil | 0.137 | 0.193 | Linoleic (44–50%) |
| Evening Primrose Oil | 0.136 | 0.192 | Linoleic (65–80%) |
| Safflower Oil | 0.136 | 0.191 | Linoleic (68–83%) |
| Butters & Semi-Solid Fats | |||
| Shea Butter | 0.128 | 0.180 | Oleic (40–55%), Stearic (35–45%) |
| Cocoa Butter | 0.137 | 0.194 | Stearic (32–37%), Oleic (30–35%) |
| Mango Butter | 0.137 | 0.193 | Stearic (35–46%), Oleic (38–48%) |
| Kokum Butter | 0.135 | 0.191 | Stearic (55–65%) |
| Cupuacu Butter | 0.130 | 0.184 | Oleic (30–35%), Stearic (30–35%) |
| Animal Fats | |||
| Lard (Pork) | 0.138 | 0.194 | Oleic (41–51%), Palmitic (25–32%) |
| Beef Tallow | 0.140 | 0.197 | Oleic (37–43%), Palmitic (24–32%) |
| Lanolin | 0.074 | 0.105 | Complex wax esters |
| Specialty Oils | |||
| Castor Oil | 0.128 | 0.180 | Ricinoleic (85–92%) |
| Jojoba Oil (Wax) | 0.069 | 0.097 | Wax esters — partially non-saponifiable |
| Neem Oil | 0.136 | 0.192 | Oleic (25–35%), Stearic (14–19%) |
| Sea Buckthorn Oil | 0.137 | 0.193 | Palmitoleic (19–45%) |
| Emu Oil | 0.137 | 0.193 | Oleic (44–54%) |
| Palm Oils | |||
| Palm Oil (Red or RBD) | 0.141 | 0.199 | Palmitic (40–48%), Oleic (36–44%) |
| Palm Olein | 0.137 | 0.193 | Oleic (40–46%) |
| Palm Stearin | 0.151 | 0.213 | Palmitic (55–70%) |
Colour guide: Green = higher SAP (more lye per gram of oil). Blue = medium SAP. Brown = lower SAP. Oils with higher SAP values require proportionally more lye — this is why coconut-heavy formulas use significantly more lye than olive oil-heavy ones.
How to Use SAP Values: The Calculation
Worked Example — Three-Oil Recipe
| Oil | Weight | NaOH SAP | Lye at 0% SF |
|---|---|---|---|
| Coconut oil | 150g (30%) | 0.190 | 28.50g |
| High oleic sunflower | 200g (40%) | 0.136 | 27.20g |
| Shea butter | 150g (30%) | 0.128 | 19.20g |
| Total oils | 500g | — | 74.90g NaOH |
Apply 5% superfat: 74.90g × 0.95 = 71.16g NaOH
Water (33% of oil weight): 500g × 0.33 = 165g distilled water
Never rely on manual calculation alone. The worked example above illustrates the concept — never use it as a production recipe without verification. Always run every recipe through the Soapmaid Lye Calculator before making any batch. A lye calculation error can result in a caustic, unsafe bar.
Understanding Superfat (Lye Discount)
Superfat is the percentage of oils in your recipe intentionally left unsaponified — free oils that remain in the finished bar as conditioning agents. A 5% superfat means you use 5% less lye than the theoretical maximum, producing a slightly richer, more conditioning bar with a built-in safety buffer.
Water Amount: Lye Concentration & Water Discount
A common starting point is water at 33–38% of total oil weight (full water). For a 500g oil batch: 500g × 0.33 = 165g water. A water discount of 10–20% produces a firmer bar that unmoulds sooner but traces faster — a challenge for intricate swirl designs. The Soapmaid Lye Calculator lets you set your desired water percentage automatically.
The Soapmaid Lye Calculator handles water calculation automatically. Select your desired water amount or lye concentration and it does the maths. Free to use, every batch.
5 Common SAP Value Mistakes
-
01
Using the Wrong Lye Type's SAP Value
Using an NaOH SAP value when making liquid soap (KOH) is a serious and common error — the batch will be severely under-lyed. Always confirm which lye type your SAP value applies to before calculating.
-
02
Not Accounting for KOH Purity
Commercial KOH is typically 90% pure. If you don't adjust for this, your batch will be under-lyed by approximately 10%. The Soapmaid Lye Calculator accounts for KOH purity automatically.
-
03
Treating SAP Values as Exact
SAP values are averages. The actual value of any oil batch varies slightly by crop origin and processing. This is why a 5% superfat is essential built-in insurance — and why you should never aim for 0% superfat in a real batch.
-
04
Forgetting to Include All Oils
Every oil in your recipe — including small amounts of castor or jojoba — needs to be included in your lye calculation. Forgetting even a minor oil can mean your batch is slightly over-lyed. Use the calculator, not mental arithmetic.
-
05
Confusing Superfat With Safety
Superfat is about skin feel and conditioning — not about making soap safe. Accurate calculation matters more than high superfat. Even a high superfat bar can be caustic if the base calculation was wrong.
Pre-Batch Safety Checklist
- Weigh all oils on a digital kitchen scale — never estimate by volume.
- Run every recipe through the Soapmaid Lye Calculator before making any batch.
- Double-check which lye type (NaOH or KOH) your calculator is set to.
- For KOH: confirm purity percentage and enter it correctly.
- Weigh your lye separately on the scale — never estimate or scoop without weighing.
- Always add lye to water — never water to lye.
- Allow your lye solution to cool to 35–45°C before combining with oils.
- Wear nitrile gloves, safety glasses, and protective clothing throughout.
- Keep children and pets completely out of your soap-making area.
- Have paper towels and clean water nearby for immediate clean-up of any spills.
Frequently Asked Questions
What is a SAP value in soap making?
A SAP value is the amount of lye required to fully saponify one gram of a specific oil. Every oil has a unique value based on its fatty acid composition. Always verify all calculations using the Soapmaid Lye Calculator.
What is the difference between NaOH and KOH SAP values?
NaOH values are for hard bar soap; KOH values are for liquid or soft soap. KOH values are approximately 1.4× higher because KOH has a higher molecular weight. Commercial KOH is also typically only 90% pure — the Soapmaid Lye Calculator handles purity adjustments automatically.
What is superfat in soap making?
Superfat is the percentage of oils intentionally left unsaponified in the finished bar — they act as conditioning agents on skin. A 5% superfat is standard for most bar soaps. Higher superfats (10–20%) are used for sensitive skin bars and 100% coconut oil formulas.
Why do SAP values vary between different oils?
Each oil has a different fatty acid composition. Shorter-chain fatty acids (like lauric acid in coconut oil) have higher SAP values — more molecules per gram means more lye needed. Longer-chain fatty acids (like oleic acid in olive oil) have lower SAP values. This is why coconut oil (0.190 NaOH) requires far more lye per gram than olive oil (0.134 NaOH).
What happens if I use too much or too little lye?
Too much lye (over-lyed): The bar will be caustic — harsh, possibly stinging, with white chalky patches. Do not use on skin. Too little lye (under-lyed): The soap won't fully saponify — soft, greasy, and won't lather properly. Both outcomes are avoided by accurate calculation with the Soapmaid Lye Calculator.
Should I always use a soap calculator even if I know the SAP values?
Yes, always. SAP values are averages and manual calculations are prone to errors. The Soapmaid Lye Calculator handles all maths automatically, accounts for superfat and KOH purity, and takes only seconds. There is no good reason not to use it every single batch.
Calculate Your Lye — Free & Instant
The Soapmaid Lye Calculator uses the SAP values from this guide to calculate your exact NaOH or KOH amounts for any recipe. Free to use, every time.
Open the Lye Calculator Free · NaOH & KOH · Superfat Adjustable · No Account NeededSource Your Soap Making Supplies
All the oils, lye, and equipment referenced in this guide — available from Soapmaid Australia.
Lye & Chemicals
Butters & Specialist Oils
Equipment & Moulds
Recipes & Lye Calculations: All recipes, formulations, usage rates, and SAP values published on this blog are provided as a general guide only. Always verify every lye calculation independently using the Soapmaid Lye Calculator before making any batch. SAP values can vary between oil batches, suppliers, and processing methods. Soapmaid Australia accepts no responsibility for any errors, omissions, or outcomes resulting from the use of recipes or calculations published on this site.
Safety & Chemicals: Soap making involves the use of sodium hydroxide (lye / caustic soda) and potassium hydroxide — both highly caustic substances capable of causing serious burns. Always wear appropriate personal protective equipment (PPE) including nitrile gloves, safety glasses, and protective clothing. Work in a well-ventilated area. Keep children and pets away from your workspace. Never use aluminium containers or utensils with lye. Store chemicals safely and in accordance with all applicable Australian state and federal regulations.
Cosmetic Compliance: Information regarding cosmetic ingredients, labelling, and regulation is provided for general educational purposes only and does not constitute legal or regulatory advice. Australian cosmetics regulations are subject to change. Always verify current requirements directly with AICIS, the ACCC, and the TGA before selling cosmetic products commercially in Australia. Soapmaid Australia is not responsible for any compliance outcomes based on information published on this blog.
Skin & Allergy Sensitivity: Every individual's skin is different. Even natural, cosmetic-grade ingredients can cause reactions in sensitive individuals. Always perform a patch test before using any new soap, cosmetic product, or formulation on a wider area of skin. If irritation, redness, or an adverse reaction occurs, discontinue use immediately and seek medical advice if necessary. Soapmaid Australia accepts no liability for adverse skin reactions arising from use of products made using ingredients or recipes featured on this blog.
Health & Therapeutic Claims: Nothing published on this blog constitutes medical advice, and no information on this site should be used to diagnose, treat, prevent, or cure any health condition. Information relating to traditional, historical, or wellness uses of ingredients is provided for general educational context only. Always consult a qualified healthcare professional before using any substance internally or for therapeutic purposes.
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General: Information on this blog is provided in good faith and is accurate to the best of our knowledge at the time of publication. Soapmaid Australia makes no warranties, express or implied, regarding the completeness or accuracy of any content. We reserve the right to update or correct content at any time without notice. Use of this information is entirely at your own risk.