What superfat percentage should I use?

Most cold process soap recipes use 3-8% superfat. A 5% superfat is the most common starting point. Higher superfat (7-8%) makes a more moisturising but softer bar. Lower superfat (2-3%) makes a harder, more cleansing bar.

Can I have 0% superfat?

Technically yes, but it is not recommended. A 0% superfat means all oils are saponified, which can make harsh soap that irritates skin. Even a 1% superfat provides a safety margin against lye-heavy soap.

Does superfat affect the soap bar quality?

Yes. Higher superfat makes soap more conditioning and moisturising but can reduce lather and make the bar softer. Very high superfat (above 8%) can also cause the excess oils to go rancid over time, especially with highly unsaturated oils.

Which oils are best for superfatting?

Oils added at trace (hot process) tend to remain unsaponified. Luxurious oils like shea butter, avocado oil, or sweet almond oil are popular superfat choices. In cold process, lye tends to saponify the higher-SAP oils first.

CraftCalcs

Superfat Calculator — Lye Adjustment for Superfat

Adjust your lye amount for the desired superfat percentage in cold process soap.

Total Oil Weight

Total weight of oils in the recipe

Lye at 0% Superfat

From SAP or Lye calculator

Superfat

Extra oil percentage beyond what lye can saponify

How We Calculate This

How the Calculation Works

Adjusted lye = lye at 0% superfat x (1 - superfat percentage / 100)

The lye reduction is the difference between the 0% superfat lye amount and the adjusted amount. The unsaponified oil weight is the oil weight x superfat percentage.

First calculate your lye at 0% superfat using the SAP Value or Lye Calculator, then use this calculator to apply your desired superfat.

Frequently Asked Questions

Related Calculators

Lye Calculator

Calculate sodium hydroxide (NaOH) or potassium hydroxide (KOH) amounts for cold process soap.

Oil Ratio Calculator

Balance your soap recipe oils for hardness, lather, conditioning and cleansing.

Fragrance Load Calculator

Work out safe fragrance or essential oil amounts for soap batches.

Mould Volume Calculator

Calculate soap mould volume and the total oil weight needed to fill it.

SAP Value Calculator

Look up and calculate saponification values for common soap-making oils.

Last updated: 2025-02-20

All calculations are estimates. Always verify quantities before purchasing materials.