Soap & Lye Calculator — Build and Resize Your Recipe

Build a soap recipe with multiple oils, adjust SAP and lye purity, resize your batch and save a complete recipe file.

My soap recipe

Build a recipe, resize the oil batch and see exactly which quantities the model asks you to weigh. Reference SAP values can be replaced with your supplier’s values.

Recipe name

Your oils

Enter oil quantities asChanging mode preserves the current composition.

Oil 1Weight · g

SAP and source · 0.19

SAP · g KOH/g oilUse g KOH/g oil: 191 mg KOH/g equals 0.191. A NaOH SAP is a different value.SAP source or batch reference

Reference SAP · SoapCalc · not a batch certificate

Oil 2Weight · g

SAP and source · 0.257

SAP · g KOH/g oilUse g KOH/g oil: 191 mg KOH/g equals 0.191. A NaOH SAP is a different value.SAP source or batch reference

Reference SAP · SoapCalc · not a batch certificate

Oil 3Weight · g

SAP and source · 0.179

SAP · g KOH/g oilUse g KOH/g oil: 191 mg KOH/g equals 0.191. A NaOH SAP is a different value.SAP source or batch reference

Reference SAP · SoapCalc · not a batch certificate

Resize oil batch to · g

Lye and water

Lye typeDual shares are chemical equivalents, not weighed-mass percentages.Lye discount · %Reduction from theoretical demand; not measured residual fat.

Purity and water settings

NaOH product purity · %Use the active alkali percentage on your supplier’s certificate.Calculate water fromSwitching mode preserves the calculated water mass.Water : weighed lye ratioBased on total weighed lye products, including impurities.

Weigh for this recipe

NaOH product70.76 g

Water141.52 g

NaOH product purity: 100% · Lye discount: 5%

500 g oils · 712.28 g fresh mixture before curing

Green: oils · coral: lye products · blue: water. Fresh mixture mass is not cured soap yield. Displayed weights are rounded; saved recipe files retain calculation inputs.

Weighed lye concentration 33.33% · active alkali 33.33% · water ratio 2:1

Reference SAP can vary between batches. Excludes additives that consume lye, premixed lye solutions and the later dilution of liquid soap.

Oil weights and SAP

Olive oil: 300 g (60%), KOH SAP 0.19 g KOH/g oil; source: https://soapcalc.net/oil-list
Coconut oil, 76°F: 150 g (30%), KOH SAP 0.257 g KOH/g oil; source: https://soapcalc.net/oil-list
Shea butter: 50 g (10%), KOH SAP 0.179 g KOH/g oil; source: https://soapcalc.net/oil-list

Kalkmi soap recipe calculator · SAP in g pure KOH/g oil · KOH/NaOH equivalent-mass ratio 1.403. Lye masses are products at the stated purities, not pure active alkali.

Load a saved Kalkmi recipe

Calculation method and reference values

Each oil weight is multiplied by its SAP, expressed as grams of pure KOH per gram of oil. Lye discount reduces that demand. NaOH equivalents use a rounded KOH/NaOH mass ratio of 1.403; each active mass is divided by its own product purity. Water ratio and concentration use weighed products. Active concentration is shown separately.

Reference coefficients: SoapCalc oil chart, checked September 27, 2026. Dual-lye and purity method: Soapy Stuff dual-lye explanation. These calculations do not measure finished-soap properties or establish a batch’s safety.