Superfat is the percentage of oils left unsaponified in your soap. A 5% superfat uses about 5% less lye than the amount that would turn every drop of oil into soap, leaving ~5% as free, conditioning oil. It is also called a lye discount. Enter your base lye and a superfat below to see the adjusted amount.
Lye at 5% superfat
95 g NaOH
| Superfat | Lye (g) | Oils left unsaponified |
|---|---|---|
| 0% | 100 | 0% of oils |
| 3% | 97 | 3% of oils |
| 5% | 95 | 5% of oils |
| 8% | 92 | 8% of oils |
Don't know your base lye? Get it from your oils with the full SoapCalc calculator, then adjust the superfat here.
Recommended superfat by soap type
| Soap | Typical superfat | Why |
|---|---|---|
| Cold-process bar (beginner) | 5% | Gentle + safety margin |
| Facial / sensitive bar | 5-8% | Extra conditioning |
| High-coconut / high-cleansing bar | 7-8% | Offsets harshness |
| Salt (spa) bar | 15-20% | Salt is drying |
| Liquid soap (KOH) | 0-3% | Excess oil clouds it |
| Laundry / cleaning soap | 0-1% | Maximum cleansing |
How superfat works
Every oil needs a specific amount of lye to saponify (its SAP value). Add up the lye for 100% of your oils, then apply the superfat: lye = base_lye × (1 − superfat/100). Less lye means some oil is never converted and stays in the bar as skin-loving free oil.
Don't go too high
More superfat is not always better. Above ~8% for everyday bars, the soap gets soft, lathers less, and is more prone to DOS / rancidity as the free oils oxidize. Match the superfat to the soap, not the maximum.
Build a full recipe in SoapCalc — it computes the lye from your exact oils at any superfat, then saves and scales the recipe.