What Oils Are Good for Soap Making: A Complete Guide to Choosing Carrier Oils?

No single oil makes a great bar — hard fats supply firmness, bubbly oils drive lather, and liquid oils add mildness, so a balanced blend of three or four beats any one carrier oil.

Each oil carries its own saponification (SAP) value — the lye needed to convert it into soap — and a bar built on the wrong combination turns out soft, drying, or rancid within weeks. Below: the oils that work, what each contributes, and the percentages experienced makers return to.

Which Carrier Oils Belong in a Soap Recipe?

Carrier oils split into three working groups, and a strong recipe draws from all three: hard fats for firmness, cleansing oils for bubbles, and liquid conditioning oils for skin feel. Relying on a single oil almost always sacrifices something.

• Olive oil is mild, conditioning, and stable. It can make up the entire formula, but traces slowly and produces a soft bar needing a longer cure. NaOH SAP ≈ 0.1355.
• Coconut oil (76°) is hard, highly cleansing, strongly bubbly. Use 15–30%; more can feel drying outside salt bars. NaOH SAP ≈ 0.178–0.1833.
• Palm oil adds hardness and creamy lather, commonly up to ~33%. Choose RSPO-certified sustainable palm. NaOH SAP ≈ 0.141.
• Tallow or lard gives hard, stable, mild, creamy bars and can be used at high percentages, including 100%. NaOH SAP ≈ 0.1405 (tallow), 0.138–0.1412 (lard).
• Castor oil improves and stabilizes bubbles but turns soft and sticky when overused; keep at 5–10%. NaOH SAP ≈ 0.128–0.1286.
• Avocado oil is conditioning and rich in unsaponifiables, commonly up to 20–30%. NaOH SAP ≈ 0.1327–0.133.
• Sweet almond oil is light and conditioning, suited to facial or sensitive-skin bars at up to ~20–30%. NaOH SAP ≈ 0.136–0.139.
• Rice bran oil conditions with more body than many liquid oils, commonly up to 30%. NaOH SAP ≈ 0.128–0.1333.
• Sunflower and canola oils are economical conditioners but soften bars at high levels; sunflower usually capped near 20%, canola near 40%. High-linoleic oils may shorten shelf life. NaOH SAP ≈ 0.1324–0.1348.
• Babassu and palm-kernel oils act like coconut — hardness, cleansing, bubbles — at up to ~25% and 20% respectively. Their higher SAP values demand careful lye math.

What Do Saponification Values Actually Tell You?

A saponification value describes the alkali required to saponify a fat or oil, usually as milligrams of KOH per gram of sample. Higher values generally mean shorter average fatty-acid chains and more alkali needed per gram. Published ranges include coconut oil at 248–265 mg KOH/g, olive oil at 184–196, palm oil at 190–209, and sunflower oil at 189–195, per the saponification value reference data.

Jojoba is a liquid wax ester, not a conventional triglyceride, so it behaves differently and carries a much lower SAP — never substitute it gram-for-gram without recalculating. Mineral oil has a saponification value of zero and is not converted into soap by alkali at all.

How Should You Build and Verify a Recipe?

Define the bar you want, then combine hard and soft oils rather than leaning on one category. Fatty-acid scores guide formulation but never guarantee skin feel.

1. Weigh every oil by mass — never by volume.
2. Enter exact oils and weights into a lye calculator; SAP values are batch averages that shift by brand and grade.
3. Use the right alkali: NaOH for solid bars, KOH for liquid soap; their SAP values differ.
4. Recalculate whenever an oil, brand, grade, or amount changes.
5. Apply a 5–8% superfat only after the recipe is calculated.
6. Cure cold-process bars until firm and mild; high-olive formulas need the longest cure.

To skip the label-reading and start from a proven list, these tested picks for soap-making oils cover the brands worth buying.

Which Oils Cause the Most Problems?

Most failed batches trace to a handful of repeatable errors. High-lauric fats — coconut, palm kernel, babassu — turn harsh past their ceilings. Sunflower, safflower, grapeseed, and hemp are oxidation-prone, so use fresh, well-stored oil and keep proportions modest. Nut oils like sweet almond require allergen labeling in commercial products, and animal fats need accurate identity, rendering quality, and transparent labeling for US buyers. Treat “carrier oil” marketing claims as marketing, not evidence of soap suitability; “natural” does not mean non-irritating. Always handle sodium hydroxide with eye protection, gloves, ventilation, and a lye-safe container — it is caustic and causes severe burns.