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What it means

Superfat (also called "lye discount") is the percentage of oils in a cold-process soap recipe that remain unsaponified (not converted to soap) at the end of the reaction. A 5% superfat means 5% of the oils stay as free oil in the final bar, buffering harshness and adding moisture.

Standard ranges: 0-2% gives a strongly cleansing, drying bar (dish soap, heavy grease hands); 3-5% is balanced for most body bars; 6-8% is moisturizing with a softer bar; 10%+ is very conditioning but soft and short-lived.

Examples

5% superfat on 1000g oils

50g free oil remains; lye reduced by enough to leave that 50g uncombined.

Do

Balance superfat to the oil profile — coconut-heavy bars handle higher superfat; olive-heavy bars stay good at 3-5%.

Don't

Exceed 10% without knowing — high superfat accelerates rancidity and makes a soft, short-shelf bar.

Calculators that use this

Soap Lye Calculator

Cold-process NaOH and water amounts for your oil blend — with superfat % for a balanced or extra-moisturizing bar.

Superfat Percentage

What 2%, 5%, or 10% superfat actually does to your soap — cleanse vs moisture tradeoff.