Saponification Calculator
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.
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.