# Saponification Calculator

Calculate NaOH and KOH amounts for soap making. Enter oil type, weight, and superfatting percentage to get precise lye and water measurements for bar.

## What this calculates

Calculate the exact amount of sodium hydroxide (NaOH) for bar soap or potassium hydroxide (KOH) for liquid soap based on your oil type, weight, and desired superfatting level. Accurate lye calculations are essential for safe, high-quality soap.

## Inputs

- **Oil Type** — options: Olive Oil, Coconut Oil, Palm Oil, Lard, Sunflower Oil, Custom SAP Value — Select the type of oil or fat used in soap making.
- **Custom NaOH SAP Value** (g NaOH/g oil) — min 0.05, max 0.35 — NaOH saponification value for custom oils (mg NaOH per g of oil).
- **Oil Weight** (g) — min 0 — Total weight of the oil or fat in grams.
- **Superfatting Percentage** (%) — min 0, max 30 — Percentage of oil left unsaponified for a milder bar (typically 3-8%).

## Outputs

- **NaOH Needed (Bar Soap)** (g) — Sodium hydroxide required for cold-process bar soap.
- **KOH Needed (Liquid Soap)** (g) — Potassium hydroxide required for liquid soap.
- **Water Needed** (g) — Water needed to dissolve the lye (approximately 30% lye concentration).
- **Total Soap Weight (Approx.)** (g) — Approximate total weight of the finished soap batch before curing.
- **SAP Value Used (NaOH)** — The NaOH saponification value used for the selected oil.

## Details

Saponification is the chemical reaction between a fat or oil and a strong alkali (lye) that produces soap and glycerin. Each oil has a unique saponification (SAP) value representing the milligrams of KOH needed to fully saponify one gram of that oil. The NaOH SAP value is derived by dividing the KOH value by 1.403.

Superfatting is the practice of using slightly less lye than needed to saponify all the oil, leaving a percentage of unreacted fat in the finished soap. This creates a milder, more moisturizing bar. Most soap makers use a superfat of 3-8%, with 5% being the most common starting point.

The water amount is calculated to achieve an approximately 30% lye concentration, which provides a good balance between working time and cure speed. After mixing, the soap undergoes saponification over 24-48 hours and then requires 4-6 weeks of curing to allow excess water to evaporate and the crystal structure to fully develop.

## Frequently Asked Questions

**Q: What is a saponification value (SAP value)?**

A: A saponification value is the number of milligrams of potassium hydroxide (KOH) required to completely saponify one gram of a specific fat or oil. Each oil has a unique SAP value based on its fatty acid profile. NaOH SAP values are obtained by dividing the KOH SAP value by 1.403.

**Q: Why do I need to superfat my soap?**

A: Superfatting leaves a small percentage of unreacted oil in the finished soap, making it milder and more moisturizing. It also provides a safety margin in case of measurement errors. A 5% superfat is the standard recommendation for most soap recipes.

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

A: Sodium hydroxide (NaOH) produces hard bar soap, while potassium hydroxide (KOH) produces soft or liquid soap. KOH requires approximately 1.403 times more alkali by weight than NaOH for the same amount of oil because of its higher molecular weight.

**Q: Can I mix different oils in one soap batch?**

A: Yes, most soap recipes use a blend of oils. Calculate the NaOH needed for each oil separately based on its weight and SAP value, then add the amounts together. Popular combinations include olive oil for mildness, coconut oil for lather, and palm oil for hardness.

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Source: https://vastcalc.com/calculators/chemistry/saponification
Category: Chemistry
Last updated: 2026-04-21