Lye Calculator
Enter your oils by weight. Lye, water and bar quality update as you type.
How the calculator works
Each oil needs a fixed amount of lye to turn fully into soap: its SAP value. The calculator multiplies each oil's weight by its SAP, adds them up, then holds back your superfat so a little oil stays free. Water is set from the lye concentration: at 33%, lye makes up a third of the solution.
Bar-quality numbers are weighted averages of each oil's fatty-acid profile. They're a guide to how a bar will feel, not a pass/fail. Read more in how to use a lye calculator and SAP values explained.
FAQ
What superfat should I use?
Five percent is a safe default for bar soap: enough unsaponified oil to be gentle, not so much that the bar goes soft or spoils early. Salt bars and 100% coconut bars often use 15–20%.
What lye concentration should I use?
Around 33% suits most cold process recipes. Higher concentrations (less water) speed up unmolding and reduce soda ash but trace faster; lower concentrations give more working time.
Can I use this for liquid soap?
Yes. Switch to KOH. The calculator assumes 90% pure potassium hydroxide, which is what most suppliers sell.