Question 1

What is a soap lye calculator?

Accepted Answer

A soap lye calculator works out the exact amount of lye and water your recipe needs to safely turn oils into soap, using each oil's saponification (SAP) value. Making soap without running the recipe through a lye calculator risks a caustic, lye-heavy bar.

Question 2

NaOH or KOH — which lye should I use?

Accepted Answer

Sodium hydroxide (NaOH) makes solid bar soap; potassium hydroxide (KOH) makes liquid or soft cream soap. This calculator supports NaOH, KOH, or a hybrid blend of both.

Question 3

What is superfat?

Accepted Answer

Superfat is the percentage of oils left unsaponified so the finished soap is more moisturizing and never lye-heavy. Around 5% is a common starting point.

Question 4

What is the difference between water:lye ratio, lye concentration, and water as a percent of oils?

Accepted Answer

They are three ways to express the same thing — how much water dissolves your lye. A 2:1 water:lye ratio is about 33% lye concentration. Switch methods in the calculator and the numbers convert automatically.

Question 5

What do the soap qualities mean?

Accepted Answer

Hardness, cleansing, conditioning, bubbly and creamy lather, and longevity are estimates from your oils' fatty-acid profile. They are guidance, not pass-or-fail targets — every soap is a balance.

Question 6

What are the default settings?

Accepted Answer

The calculator opens with common starting points you can keep or change: 5% superfat, a 2:1 water:lye ratio, and NaOH (for solid bar soap), at a 1000-gram batch. These are typical defaults many soapmakers begin from — adjust them to suit your oils and process.

Question 7

What lye purity does this calculator assume?

Accepted Answer

It uses the standard soapmaking values — 100% NaOH and 90% KOH. In practice NaOH is usually sold at 97–100% and KOH around 90%, so if your lye's purity is different, your numbers change slightly. The SoapCalc Pro app lets you set exact purity to match your label.

Question 8

Can I work in ounces or grams?

Accepted Answer

Both. Toggle g or oz next to Total oils and every amount converts.

Question 9

Is the calculator free? Do I need an account?

Accepted Answer

Yes, it is completely free with no sign-up.

Question 10

Is this the same as the SoapCalc Pro app? Are my recipes linked?

Accepted Answer

The web calculator is a free standalone tool for quick lye math — no account, and it does not sync with the app. Recipes you enter here are not saved to an app account, and app recipes do not appear here. The SoapCalc Pro app for iOS and Android is a separate, fuller product that saves recipes, syncs across your devices, troubleshoots batches, and helps you build and adjust recipes.

Question 11

Did the creators approve their recipes being here?

Accepted Answer

All starter recipes are classic, widely-used formulas included for reference.

Soap Recipe Calculator

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