Soap Lye Calculator

Enter your recipe, choose NaOH or KOH, set superfat and water. Results update instantly. You can switch units, share the URL, save/load recipes, search oils, and print a clean recipe sheet.

Step 1 · Choose your lye
Step 2 · Set your batch size
Optional · Bar calculator
When both fields are set, Weight of oils auto-updates to —.
Step 3 · Dial in your water
Water method
Step 4 · Finish tweaks

Fragrance helper (optional)

Fragrance amount
—

Always follow supplier IFRA limits.

Step 5 · Add oils from the library

Tip: You can still adjust percentages below. The total should be ~100%.

Step 6 · Build your oil list

Oils 0%

Recipe notes

Notes are saved with recipes and included in print.

Results

Required lye
—
Water
—
Total batch
—
Per‑oil weights
Oil%Weight
Totals

Profile (derived)

Hardness (29–54)
—
Cleansing (12–22)
—
Conditioning (44–69)
—
Bubbly (14–46)
—
Creamy (16–48)
—
Iodine (41–70)
—
INS (136–165)
—
Sat : Unsat
—

Fatty acids (One vs All)

Fatty acidOne (%)All (%)
Lauric——
Myristic——
Palmitic——
Stearic——
Ricinoleic——
Oleic——
Linoleic——
Linolenic——
Sat——
Mono——
Poly——
Base SAP (NaOH)
—
Base SAP (KOH)
—
Blend SAP (NaOH)
—
Blend SAP (KOH)
—
Disclaimer: This tool is for informational purposes only. Always verify calculations, use proper PPE, and follow safe soaping practices.

Frequently asked questions

What’s the difference between NaOH and KOH?
Sodium hydroxide (NaOH) is for bar soap. Potassium hydroxide (KOH) is for liquid soap and paste soaps. Choose KOH only when making liquids; then set the KOH purity to match your flakes.
Which KOH purity should I use?
Many store‑bought KOH flakes are ~90%. The calculator adjusts lye weight automatically based on the purity you select.
Water % vs. lye concentration vs. water:lye — which should I use?
Beginners often start with water % of oils. For more control, use lye concentration (%) or a water:lye ratio (e.g., 2.5:1). All three modes produce the same underlying calculation.
What superfat should I choose?
3–7% is common for bar soap. Higher superfat can feel more conditioning but may soften bars and slow cure. Pick based on your oils and goals.
Can I save, load, and share recipes?
Yes. Saved recipes are stored in your browser (localStorage). Share the exact recipe with the copy‑link button or QR code. No account is required.
Do you store my data or track recipes?
No. Recipes you save remain on your device. Only URLs you choose to share leave your browser.
How accurate are SAP values and results?
SAP and fatty‑acid data come from reputable sources and industry norms, but natural oils vary by source and batch. This tool is for planning—always test and follow safe soaping practices.
How do I print a clean recipe sheet?
Use Print or Quick Print in the actions panel. The page includes a print‑optimized layout and optional sections you can toggle.