Soap Making Lye Calculator

Calculate exact NaOH and KOH amounts for cold process and liquid soap. Select your oils, set your superfat, and get your recipe instantly.

Your Oils

Settings

0% (no superfat) 20% (extra moisturizing)

Recipe Results

Add oils and enter weights to see your recipe.

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Soap Making Reference

Common Bar Soap Oils

  • Coconut Oil (76°) Hard, bubbly lather
  • Olive Oil Gentle, conditioning
  • Palm Oil Hardness, stable lather
  • Shea Butter Creamy, moisturizing
  • Castor Oil Lather booster

Specialty & Luxury Oils

  • Avocado Oil Rich, conditioning
  • Cocoa Butter Hard bar, chocolatey
  • Mango Butter Creamy, silky feel
  • Hemp Seed Oil Light, absorbent
  • Jojoba Oil Closest to skin sebum

Animal Fats for Soap

  • Lard (Pork) Creamy, hard bar
  • Tallow (Beef) Very hard, white bar
  • Goat Milk Fat Extra gentle
  • Beeswax Hardener (use sparingly)

Superfat Guidelines

  • 0% Laundry / cleaning soap
  • 3-5% Standard body bar
  • 5-8% Moisturizing bar
  • 8-15% Very gentle / facial bar
  • 15-20% Super-fatted, soft bar

Frequently Asked Questions

What is the difference between NaOH and KOH in soap making?

NaOH (sodium hydroxide) is used to make solid bar soap through cold process or hot process methods. KOH (potassium hydroxide) is used to make liquid soap. Each oil requires a different amount of lye depending on its saponification (SAP) value. The KOH amount is approximately 1.403 times the NaOH amount for the same oil.

What does superfat mean in soap making?

Superfat is the percentage of oils in your recipe that will not be converted to soap. A 5% superfat (the most common default) means 5% of your oils remain as free oils in the finished bar, making it more moisturizing and gentle on skin. Higher superfat percentages make softer, more conditioning bars. Lower superfat makes a harder, more cleansing bar.

What water-to-lye ratio should I use for cold process soap?

The most common water-to-lye ratio is 2:1, meaning two parts water for every one part NaOH. A lower ratio (like 1.5:1) produces a harder bar faster and reduces curing time, but the soap traces more quickly, giving you less working time. A higher ratio (like 3:1) gives more working time but takes longer to cure.

How do I use a lye calculator for soap making?

Select the oils you want in your recipe, enter the weight of each oil, set your desired superfat percentage (typically 5%), choose your water-to-lye ratio (typically 2:1), and the calculator will tell you exactly how much NaOH (for bar soap) or KOH (for liquid soap) and water you need. Always measure lye by weight, not volume, and use a digital scale accurate to 0.1 grams or 0.1 ounces.