🧼

Soap Lye Calculator

150+ oils, fats & waxes · NaOH & KOH · Bar & Liquid soap

1. Type of Lye
2. Weight of Oils
Total (auto-calculated): 0.000 oz
Enter individual oil weights in the recipe table below. The total updates automatically.
3. Water
%
38% is the recommended starting point for beginners.
4. Additional Settings
%
oz/lb
oz
5. 🧴 Additives
Clays, micas, botanicals, exfoliants, etc. Amounts are for reference — not included in lye calculations.
Additive Name Amount Unit
📋 Recipe Summary
Item lb oz g
Water———
Lye (NaOH)———
Oils (total)———
Fragrance———
Total Batch———
📊 Soap Bar Qualities
Quality Range Val Status
🧪 Fatty Acid Profile
Sat : Unsat —
6. Select Oils, Fats & Waxes
NaOH SAP
—
KOH SAP
—
Sat : Unsat
—
Double-click an oil to add it, or use the button above
🫙 7. Recipe Oils — up to 14 oils 0.00%
# Oil / Fat / Wax % of Oils Weight (oz) NaOH (g)
TOTALS 0.00% 0.000 —
8. 📋 Recipe at a Glance
Property Value
Weights
Total Oil Weight—
Water—
Lye—
Fragrance Weight—
Total Batch—
Recipe Settings
Water as % of Oils—
Lye Concentration—
Water : Lye Ratio—
Super Fat—
Fragrance Ratio—
Oil Profile
Sat : Unsat—
Iodine—
INS—
📝 Recipe Notes
Notes are saved with Export JSON and included in View Recipe Summary, Save .txt, and Print.
Oil / Fat / Wax ↕ NaOH SAP ↕KOH SAP ↕ Iodine ↕INS ↕ Lauric ↕Myristic ↕ Palmitic ↕Stearic ↕ Ricinoleic ↕Oleic ↕ Linoleic ↕Linolenic ↕

How to Use This Calculator

1. Recipe Settings
Lye type — NaOH for bar soap, KOH for liquid soap. Check "90% KOH" if your KOH is 90% purity.
Total oil weight — enter in lb, oz, or g. Everything scales from this value.
Water — 38% of oils is beginner-safe. Experienced soapers reduce to 32–33%.
Lye Concentration mode — sets lye as % of the lye+water solution directly.
Water:Lye Ratio mode — sets the ratio of water to lye (e.g. 2.3 means 2.3× water vs lye).
Super fat % — 5% is standard. Higher = more skin-conditioning free oil in the bar.
Fragrance — 0.5 oz/lb typical; essential oils usually lower.
2. Selecting Oils (Browser)
Click any oil in the browser list to preview its individual properties in the One column.
Double-click or press "+ Add to Recipe" to add it to the next empty recipe slot.
You can also use the dropdown in each row to directly select or change an oil.
One = properties of the currently selected oil. All = weighted average for your full recipe.
3. Entering Oil Amounts (Tri-directional)
Each row has three inputs: %, Oz, and Grams. Edit any one — the others update automatically. All percentages must total 100%.
4. Soap Bar Qualities Reference
Hardness (29–54) — firmness of the finished bar.
Cleansing (12–22) — ability to remove oils/dirt. Too high = drying to skin.
Conditioning (44–69) — moisturising level deposited on skin.
Bubbly (14–46) — big, fluffy, fast-forming bubbles.
Creamy (16–48) — stable, lotion-like creamy lather.
Iodine (41–70) — degree of unsaturation. Lower = harder bar. Above 70 may be too soft.
INS (136–165) — overall bar quality gauge; ideal is around 160.
⚠ Safety
Lye (NaOH/KOH) is caustic and can cause serious burns. Always wear gloves and eye protection. Always add lye to water — never water to lye. Keep children away from your workspace. This calculator is for reference — always verify your formula before use.