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Soap Calculator

Calculate exact lye (NaOH/KOH) and water amounts for cold or hot process soap making. Add your oils, set superfat, and get a full recipe breakdown.

⚠️ Lye is caustic. Always add lye to water (never water to lye). Wear PPE. Use exact measurements.

Recipe Settings

Choose soap type, lye, and batch size

5%

0% = full saponification · 5–8% = typical · 20% = very moisturizing

33%

25–38% typical for bar soap

Oils & Fats

Add oils with weights — SAP values auto-applied

Total Oil Weight
0 g
Oil / FatWeightUnit

Quick Recipe Presets

NaOH (Lye)
—
grams
Water
—
grams
Total Oil Weight
—
grams
Superfat
—
% unreacted oil
Lye Concentration
—
lye ÷ (lye + water)
Estimated Batch Size
—
total recipe weight

SAP Value Reference

Coconut Oil

NaOH: 0.190 · KOH: 0.268

Olive Oil

NaOH: 0.134 · KOH: 0.188

Palm Oil

NaOH: 0.141 · KOH: 0.199

Castor Oil

NaOH: 0.128 · KOH: 0.180

Shea Butter

NaOH: 0.128 · KOH: 0.180

Sunflower Oil

NaOH: 0.134 · KOH: 0.188

Lard

NaOH: 0.138 · KOH: 0.194

Tallow (beef)

NaOH: 0.140 · KOH: 0.197