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Soap Lye Calculator
Estimate lye and water for bar or liquid soap from multiple oil weights, SAP values, and superfat. Includes visible purity assumptions and safety guidance.
This works right here on your device — nothing gets sent out.
| Oil | Weight (g) | % |
|---|
Calculated lye
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Suggested water
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Total oils
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Uses approximate SAP values for the listed oils, a 33% lye concentration, and 97% NaOH / 90% KOH purity assumptions. Actual SAP values vary by supplier and batch; verify with a trusted calculator before use.
How it works
- Choose NaOH or KOH, set the target oil weight and superfat.
- Enter the weight of each oil; the calculator applies its listed SAP value.
- Review the estimated lye and water amounts, then verify independently before making soap.
FAQ
Is this recipe safe to use without checking it?
No. Lye is caustic and SAP values vary by oil supplier and batch. Treat the result as a starting estimate and verify it with a trusted soapmaking calculator before use.
What is superfat?
Superfat reduces the calculated lye amount so some oils remain unsaponified. The default here is 5%, a common starting point, but it is not a safety guarantee.
Does this calculate both bar and liquid soap?
Yes. Choose NaOH for bar soap or KOH for liquid soap. The KOH result uses a 90% purity assumption.
How we compare
| Feature | Online Tool Store | SoapCalc | Bramble Berry Lye Calculator |
|---|---|---|---|
| NaOH and KOH modes | Yes | Yes | Yes |
| Multiple oil inputs | Yes | Yes | Yes |
| Copyable recipe output | Yes | Varies | Varies |
| Safety assumptions shown | Yes | Yes | Yes |
Use this for a quick local estimate, then cross-check the recipe in an established soapmaking calculator before handling lye.