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Soap Making Calculator

Calculate precise lye and water amounts for handmade soap recipes. Enter your oils and superfat percentage to get accurate NaOH or KOH measurements.

Calculate Soap Recipe

Oils & Fats

Recommended: 5-8%

Typical: 33-38%

Recipe Results

🧪 Required Materials (NaOH)

Lye Amount
140.7
grams
Water Amount
330.0
grams
Total Oils
1000.0 grams
Batch Weight
1470.7 grams
Superfat
5% (50.0 grams)
Water Ratio
33%

📊 Oil Breakdown

Coconut Oil200.0 grams (20.0%)
Olive Oil500.0 grams (50.0%)
Palm Oil300.0 grams (30.0%)

💡 Recommendations

  • ✅ Recipe looks balanced! Remember to wear safety gear when handling lye.

⚠️ Safety Warning

  • • Always wear safety goggles, gloves, and long sleeves
  • • Work in well-ventilated area
  • • Add lye to water (never water to lye) to prevent splashing
  • • Keep vinegar nearby to neutralize lye spills

Related Calculators

Common Oils SAP Values

Oil/ButterNaOH SAP (Bar Soap)KOH SAP (Liquid Soap)Properties
Coconut Oil0.1900.266Bubbles, cleansing, hardness
Olive Oil0.1350.189Conditioning, mild, stable
Palm Oil0.1420.199Hardness, creamy lather
Castor Oil0.1280.179Boosts lather, moisturizing
Shea Butter0.1280.179Creamy, conditioning
Cocoa Butter0.1370.192Hardness, long-lasting

SAP Value: Milligrams of lye needed to saponify 1 gram of oil. Always recalculate when changing oils.

Superfat Percentage Guide

0-3% Superfat

Result: Harsh, drying soap with excess cleansing

Use for: Laundry soap, heavily soiled hands (mechanics)
Not recommended for: Body/face soap, sensitive skin
Note: Risk of lye-heavy soap if measurements are off

5-8% Superfat (Recommended)

Result: Balanced, skin-friendly soap with good lather

Use for: All-purpose body soap, face bars, daily use
Benefits: Safety margin against lye excess, mild cleansing, long shelf life
Best for: Beginners and most recipes

10-15% Superfat

Result: Very moisturizing, softer soap

Use for: Dry skin, luxury bars, shampoo bars
Caution: Shorter shelf life (6-12 months), may not lather well, can feel oily
Storage: Keep in cool, dry place to prevent DOS (rancidity)

15-20% Superfat

Result: Extremely soft, oily bars (not recommended)

Issues: Won't harden properly, poor lather, short shelf life (3-6 months)
Rancidity risk: High - unsaponified oils oxidize quickly
Only use if: Making lotion bars or specialty products (not true soap)

Step-by-Step Soap Making Process

1
Prepare Workspace & Safety Gear

Put on goggles, gloves, long sleeves. Clear workspace. Have vinegar ready for spills. Open windows for ventilation.

2
Measure Oils & Heat

Weigh all oils precisely. Melt solid oils (coconut, palm) to 100-110°F. Mix with liquid oils.

3
Mix Lye Solution

Add lye slowly to water (NEVER reverse!) in well-ventilated area. Stir until dissolved. Cool to 100-110°F.

4
Combine Oils & Lye

When both at 100-110°F, pour lye solution into oils. Stick blend in short bursts (5 sec blend, 10 sec stir).

5
Blend to Trace

Continue blending until "trace" - mixture thickens like pudding. Light trace: thin, pourable. Thick trace: holds shape.

6
Add Fragrance & Pour

Add essential oils/fragrance at trace. Stir thoroughly. Pour into mold. Tap to remove air bubbles.

7
Insulate & Saponify

Cover mold with plastic wrap, then towels. Let sit 24-48 hours for gel phase and saponification.

8
Unmold & Cure

Unmold after 24-48 hrs. Cut into bars. Cure on rack in cool, dry place for 4-6 weeks. Turn weekly for even drying.

Oil Properties & Benefits

🥥 Coconut Oil (20-30%)

Properties: Hard bar, big bubbles, cleansing
Caution: Over 30% can be drying. Use 76° refined for consistency.

🫒 Olive Oil (30-100%)

Properties: Mild, conditioning, stable lather
100% Castile: Slimy lather, needs 6-12 month cure. Mix with other oils for balance.

🌴 Palm Oil (20-40%)

Properties: Hard bar, creamy lather, white color
Alternative: Lard, tallow, babassu (sustainable palm certified only)

🌰 Castor Oil (5-10%)

Properties: Lather booster, draws moisture, soft
Sweet spot: 5% enhances bubbles. Over 10% = sticky, soft soap.

🧴 Shea Butter (5-15%)

Properties: Creamy lather, skin conditioning, hard
Use unrefined: More nutrients. Doesn't add much lather but great for skin.

🍫 Cocoa Butter (5-15%)

Properties: Very hard bar, long-lasting, stable
Benefits: Prevents DOS, adds hardness. Deodorized if you don't want chocolate scent.

Safety & Troubleshooting

⚠️ Critical Safety Rules

  • • Always add lye to water - Never reverse (causes volcanic eruption and burns)
  • • Work in ventilated area - Lye fumes are caustic and can burn airways
  • • Wear full PPE - Goggles, gloves, long sleeves, closed-toe shoes
  • • Keep vinegar nearby - Neutralizes lye spills (pour over affected area)
  • • No distractions - Children, pets, phones away during lye handling
  • • If lye contacts skin - Rinse with water for 15 minutes, seek medical attention
Soap Won't Trace

Causes: Wrong temperature, mismeasured lye, old lye
Fix: Keep blending, check recipe calculations, test lye freshness

Soap Seized (Too Fast)

Causes: Fragrance oil, too much sugar, overheating
Fix: Hot process the batch, or add water and rebatch

Soft Soap Won't Harden

Causes: High superfat, not enough hard oils, too much water
Fix: Longer cure (8-12 weeks), add more coconut/palm next batch

DOS (Orange Spots)

Causes: Rancid oils, high superfat, metal contamination
Prevention: Fresh oils, 5-8% superfat, add ROE (antioxidant)

Beginner-Friendly Recipe Formulas

🧼 Classic Beginner Recipe (Hard, Bubbly Bar)

• Coconut Oil: 25%
• Palm Oil: 25%
• Olive Oil: 45%
• Castor Oil: 5%
Superfat: 5% | Water: 33% | Cure: 4-6 weeks

Balanced lather, hardness, and skin-friendliness. Great first recipe.

🌿 Gentle Bastile (Sensitive Skin)

• Olive Oil: 70%
• Coconut Oil: 20%
• Cocoa Butter: 5%
• Castor Oil: 5%
Superfat: 8% | Water: 35% | Cure: 6-8 weeks

Mild, conditioning bar. Good for dry or sensitive skin.

💪 Shampoo Bar (Hair Care)

• Coconut Oil: 30%
• Olive Oil: 30%
• Castor Oil: 15%
• Shea Butter: 15%
• Jojoba Oil: 10%
Superfat: 10% | Water: 33% | Cure: 6 weeks

Gentle cleansing with conditioning oils. Follow with vinegar rinse.

Frequently Asked Questions

How do I calculate lye for soap making?
Multiply each oil weight by its SAP (saponification) value, then sum totals. For bar soap use NaOH SAP values; for liquid soap use KOH values. Apply superfat discount (typically 5-8%) by reducing lye amount. Example: 500g olive oil × 0.135 NaOH SAP = 67.5g NaOH needed. With 5% superfat: 67.5 × 0.95 = 64.1g NaOH final amount. Each oil has unique SAP value - coconut (0.19), palm (0.142), castor (0.128).
What is superfat and why is it important?
Superfat is extra oil (5-20%) left unsaponified to ensure all lye reacts and create moisturizing soap. 5-8% superfat: balanced, skin-friendly bar soap. 10-15%: extra moisturizing, softer soap, shorter shelf life. 0-3%: harsh, drying soap (not recommended). 15-20%: very soft, oily soap that may not lather well. Reduce lye by superfat percentage, not increase oils. Too much superfat causes DOS (dreaded orange spots) from rancid oils.
How much water should I use for soap making?
Water amount: 33-38% of total oil weight for most recipes. 33% (1:1 lye to water): fast trace, less warping, shorter cure. 38% (full water): slower trace, easier for swirls, longer cure time. Cold process: 33-38% water. Hot process: 25-33% (uses heat). Goat milk/beer: Replace part or all water, freeze first. Calculate: 500g oils × 0.33 = 165g water minimum. Or use lye concentration: 33% lye to 67% water (1:2 ratio).
Can I substitute oils in a soap recipe?
Yes, but properties change. Match oil categories: Hard oils (coconut, palm) for hardness/lather. Soft oils (olive, sunflower) for conditioning. Luxury oils (castor, shea) for specific benefits. Never exceed 30% coconut (drying). Replace palm with lard/tallow/babassu 1:1. Replace olive with rice bran/sunflower (similar SAP). Recalculate lye - different oils = different SAP values. Use soap calculator to verify safety. Small changes OK, major swaps need recalculation.
What are the best oils for soap making?
Base oils (60-70%): Olive (mild, conditioning), Palm (hard bar, sustainable certified only), Lard/Tallow (economical, hard). Hard oils (20-30%): Coconut (bubbles, cleansing, max 30%), Babassu (coconut alternative). Conditioning (5-15%): Shea butter (creamy lather), Cocoa butter (hard, conditioning), Avocado (rich, moisturizing). Special (3-10%): Castor (boosts lather, 5% ideal), Jojoba (luxury, doesn't saponify well). Balanced recipe: 25% coconut, 50% olive, 20% palm, 5% castor.
How long does handmade soap need to cure?
Minimum cure time: 4-6 weeks for most cold process soap. Factors affecting cure: Water content (more water = longer cure). Oil type (olive 100% = 6-12 months, coconut/palm = 4 weeks). Superfat level (high superfat = longer cure). Salt/milk bars = 8-12 weeks. Hot process: 1-2 weeks (cooked but still needs water evaporation). Test cure: Weigh bar weekly - fully cured when weight stabilizes. pH test: 9-10 is safe (pure lye-free soap). Longer cure = harder, milder, longer-lasting soap.
What safety equipment do I need for soap making?
Essential safety gear: Safety goggles/face shield (splash protection). Chemical-resistant gloves (nitrile or rubber, not latex). Long sleeves and pants (cover skin). Closed-toe shoes. Well-ventilated area (lye fumes). Keep on hand: White vinegar (neutralizes lye spills). Running water (rinse if lye contacts skin). First aid kit. Never use aluminum (reacts with lye). Use stainless steel, glass, or plastic. Add lye to water slowly (NEVER reverse - causes eruption). Work near sink. Keep children and pets away.