Free Tool for Soap Makers
Lye Calculator
Calculate exact NaOH (bar soap) and KOH (liquid soap) amounts for any oil blend. Superfat, water discount, and KOH purity adjustments included.
1 Add Oils to Your Recipe
No oils added yet. Start building your recipe above.
2 Settings
3 Your Results
NaOH — Bar / Hard Soap
—
grams NaOH (100% pure)
—
g water
KOH — Liquid / Paste Soap
—
grams KOH (at 90% purity)
—
g water
Oil Breakdown
⚠️ Always verify with a second calculator before making soap. Lye is caustic — safety goggles and gloves required.
SAP Value Reference Chart — 40 Oils
Saponification chart for soap makers. SAP values show how much lye (NaOH or KOH) is needed per gram of oil. Formula: Lye (g) = Oil weight (g) × SAP value. Water: 33–38% of NaOH weight. Oils available from Sekiya Sourcing are highlighted.
| Oil | NaOH SAP | KOH SAP |
|---|
What is Superfat?
Superfat (lye discount) is the % of oils left unsaponified. 5% is standard for skin-care bars — it makes the soap more conditioning and provides a safety margin for lye inaccuracies. Shampoo bars: 0–2%. Face soap: 5–8%. Body soap: 5%.
NaOH vs KOH
NaOH (sodium hydroxide) makes hard bar soap. KOH (potassium hydroxide) makes soft paste or liquid soap. KOH values are ~40% higher than NaOH because of molecular weight difference. Commercial KOH is usually 90% pure — adjust accordingly.
Water Discount
Water (as % of NaOH weight): 33% gives a harder bar that cures faster. 38% is easier to work with but takes longer to harden. For swirl designs, use 33%. For hot process soap, 33% or less. Never use distilled water less than 25%.