This is a free soap calculator — no account needed to calculate.Add your oils and their percentages, set the total oil weight, superfat, and lye type, and it calculates the lye (NaOH or KOH), the water, and a full quality profile for the bar you're designing.
Oils & butters
70%NaOH lye
91.9 g
Water
186.6 g
How is soap lye calculated?
SoapPilot multiplies each oil's weight by its NaOH or KOH SAP value, sums the results, then applies the selected superfat. The formula is final lye = Σ(oil weight × SAP value) × (1 − superfat/100). Use one weight unit consistently. The oil catalog exposes the SAP values used for each ingredient; changing an oil, lye type, weight, or superfat changes the result.
How are water and lye concentration related?
Lye concentration is lye divided by lye plus water. When concentration is the selected method, water is calculated as water = lye × (1 / concentration − 1). A 33% concentration is about a 2.03:1 water-to-lye ratio. Water as a percentage of oils is a different method and can produce a different concentration for each recipe. See the water and lye ratio guide before discounting water.
What do the soap quality scores mean?
The scores are formulation indicators derived from the selected oils' fatty-acid profiles; they are not laboratory test results. Hardness, cleansing, conditioning, bubbly, creamy, and longevity help compare versions of a formula. Iodine and INS are additional formulation indicators. Ingredient quality, process, cure, additives, storage, and testing still affect the finished soap.
Does a correct calculator result make soap safe?
No. A calculator checks formulation arithmetic; it does not certify a batch or replace safe handling, supplier documentation, or finished-product testing. Sodium and potassium hydroxide are caustic. Confirm the lye type, supplier-stated lye purity, units, every oil weight, superfat, and liquid setting before mixing. Follow the product safety data sheet and the full SoapPilot safety guidance.
What are this calculator's limits?
The result is a formulation estimate, not a safety certification. SAP values are reference values and natural oils can vary. The calculation cannot detect a mislabeled ingredient, an inaccurate scale, a data-entry error, lye purity that differs from the selected setting, or a production mistake. Recalculate after every substitution or scale change and independently review any formula before production or sale.
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