Free Soap & Lye Calculator - Calculate Your Soap Recipe
Plan safer, better homemade soap batches with a beginner-friendly mode and a detailed advanced mode.
Recipe Inputs
Mild cleanse with creamy lather.
Auto oil blend
Live Results
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Step-by-Step DIY Process
This process is auto-generated from your current values and updates every time you tweak the recipe.
- 1Safety first: wear goggles, gloves, long sleeves, and work in a ventilated area. Keep children and pets away.
- 2Prepare and weigh all ingredients precisely using a digital scale. Oils total: 1000.0 g.
- 3Oil blend to measure: Olive Oil: 450.0 g Coconut Oil (76 deg): 250.0 g Palm Oil: 200.0 g Castor Oil: 50.0 g Shea Butter: 50.0 g
- 4Slowly sprinkle 139.7 g of NAOH into 330.0 g distilled water. Never pour water into lye.
- 5Stir lye solution until fully dissolved. Let it cool to around 32-43 C (90-110 F). Current lye concentration target: 29.7%.
- 6Melt hard oils/butters first, then add liquid oils. Bring oils to a similar temperature range of 32-43 C (90-110 F).
- 7Pour lye solution into oils and blend to light trace using short bursts with a stick blender, alternating with hand stirring.
- 8At light trace, optionally add fragrance, color, or botanicals in small amounts and mix gently.
- 9Pour batter into mold, tap to release air bubbles, texture top if desired, and insulate lightly if needed.
- 10Unmold after 24-48 hours (longer if soft), then cut bars and cure for 4-6 weeks in a cool, dry, ventilated place.
- 11Before regular use, pH-test and patch-test your finished soap. Estimated final batch size: 1469.7 g.
Boost Lather
Try 3-6% sugar solution, 3-8% castor oil, or a little coconut milk for creamier bubbles.
Make It Gentler
Use oats, kaolin clay, aloe juice, or goat milk. Keep fragrance low for sensitive skin bars.
Improve Hardness
Add sodium lactate (1-3%), stearic-rich butters, and allow a full cure for longer-lasting bars.
Beginner and Advanced Quick Guide
Beginner mode gives easy presets and safe defaults. Advanced mode lets you control every oil, superfat, water method, and additive estimate.
Beginner mode best for
First 5-10 batches, quick recipe drafts, and safer default settings.
Advanced mode best for
Custom blends, nuanced water control, and production-style repeatability.
Soap Making Calculator: Your Ultimate DIY Guide
Whether you're a complete beginner starting your first cold process soap batch or an advanced soap maker perfecting custom formulations, our free online soap and lye calculator simplifies the chemistry of saponification. Calculate precise quantities of sodium hydroxide (NaOH) or potassium hydroxide (KOH), determine the perfect water-to-lye ratio, and adjust superfat percentages for the exact soap properties you want.
Beginner-Friendly Features
- ✓Pre-built soap recipes: Balanced everyday bar, sensitive skin, and bubbly spa formulas
- ✓Automatic calculations: No manual math—adjust sliders and watch results update instantly
- ✓Step-by-step guides: Generated DIY process for every recipe you create
- ✓Safety reminders: Integrated safety tips throughout the calculation process
Advanced Soap Maker Tools
- ✓Custom oil blending: Add, remove, or adjust individual oils and weights
- ✓Flexible lye types: Choose NaOH for bars or KOH for liquid soap
- ✓Water control methods: Set by lye ratio or percentage of oils
- ✓Additive calculations: Estimate fragrance, mica, clays, and other inclusions
Understanding Soap Making Chemistry
What Is Saponification?
Saponification is the chemical reaction between fats (oils and butters) and lye (sodium or potassium hydroxide). This calculator automatically handles the complex stoichiometry, using each oil's unique saponification value (SAP value) to determine exactly how much lye is needed to convert your oils into soap.
Superfat: The Key to Mild Soap
Superfat (also called free fatty acid or FFA) is intentionally unsaponified oil left in your soap. A typical range is 3–9%:
- 3% superfat: Clean-cleansing, longer shelf life
- 5% superfat: Balanced everyday bar (most popular)
- 8–10% superfat: Extra conditioning for sensitive or dry skin
Why Oil Choice Matters
Each carrier oil contributes unique properties to your finished soap. Olive oil creates a creamy lather and is moisturizing. Coconut oil provides abundant fluffy lather and hardness but can be drying. Palm oil adds hardness and stability. Castor oil boosts lather and conditioning. Our calculator includes seven common oils with accurate SAP values (both NaOH and KOH) to ensure your recipe success.
NaOH vs. KOH: Bar Soap vs. Liquid Soap
NaOH (Sodium Hydroxide): Creates solid, hard bars. Favored by cold process soap makers. Required for traditional bar soap recipes.
KOH (Potassium Hydroxide): Creates liquid soap. Softer and more soluble in water than NaOH. Perfect for liquid soap, shampoo bars, and creamy formulations.
Common Soap Making Questions Answered
How accurate is this soap calculator?▼
Our soap calculator uses scientifically accurate saponification values for each oil and industry-standard formulas. It matches professional soap-making software results. However, always do a small test batch first and adjust based on your experience.
What water-to-lye ratio should I use?▼
A ratio of 1.7:1 to 2.5:1 (water to lye) is standard. Lower ratios (1.7–2.0) make thicker, faster trace. Higher ratios (2.3–2.5) give more working time. Our calculator handles both approaches for flexibility.
Can I scale this recipe up or down?▼
Absolutely. In Beginner mode, adjust the "Total Oils (g)" slider to scale the entire recipe. In Advanced mode, edit individual oil weights directly. Percentages stay constant while actual grams scale proportionally.
How long does cold process soap take to cure?▼
Typically 4–6 weeks minimum for cold process soap to fully cure and harden. During cure, water evaporates and alkali (unused lye) continues to neutralize, resulting in a gentler, harder bar. Some soaps benefit from 8–12 weeks of cure for maximum hardness.
Should I use a trace calculator too?▼
Our calculator handles ingredient quantities only. For predicting trace speed (thickening), you'll need additional tools or experience. Factors like temperature, blender speed, stick-blending duration, and fragrance all affect trace timing.