Calculator Form
Example Data Table
| Oil | Amount | NaOH SAP | KOH SAP | Purpose |
|---|---|---|---|---|
| Olive Oil | 500 g | 0.134 | 0.188 | Conditioning base |
| Coconut Oil | 250 g | 0.183 | 0.257 | Cleansing and bubbles |
| Shea Butter | 150 g | 0.128 | 0.180 | Creamy hardness |
| Castor Oil | 100 g | 0.128 | 0.180 | Lather support |
Formula Used
Total oil weight = sum of all oil amounts converted to grams.
Full NaOH need = oil weight × NaOH SAP value.
Full KOH need = oil weight × KOH SAP value.
Pure NaOH = full NaOH need × NaOH share × (1 − superfat).
Pure KOH = full KOH need × KOH share × (1 − superfat).
Actual lye = pure lye amount ÷ lye purity.
Water by concentration = total actual lye × ((100 − concentration) ÷ concentration).
Water by ratio = total actual lye × selected water ratio.
Water by oil percent = total oil weight × selected water percent.
Batch total = oils + actual lye + water + fragrance + additives.
How to Use This Calculator
- Select the unit used for your oil amounts.
- Enter your superfat, lye split, and lye purity values.
- Choose the water method that matches your recipe style.
- Add each oil amount and select the oil name.
- Use custom SAP fields for oils not listed.
- Enter fragrance, additives, and expected batch loss.
- Press the calculate button.
- Review the result above the form.
- Download the CSV or PDF report for your records.
Always follow proper lye safety steps. Wear gloves and eye protection. Add lye to water slowly. Never pour water into dry lye.
Understanding Dual Lye Soap Planning
A dual lye recipe uses both sodium hydroxide and potassium hydroxide. Sodium hydroxide helps create a firmer bar. Potassium hydroxide adds solubility and a creamier feel. Makers use this method for shave soap, hybrid soap, and softer specialty batches.
Why the Ratio Matters
The alkali split changes texture. A high sodium share gives more hardness. A higher potassium share can improve spread and lather. The best ratio depends on the purpose of the soap. A shave puck may need more potassium. A bath bar may need only a small potassium share.
Oil Selection and SAP Values
Each oil needs a different amount of alkali. This number is called the SAP value. Coconut oil, olive oil, tallow, castor oil, and shea butter all behave differently. The calculator uses separate sodium and potassium SAP values. You can also enter custom values when your supplier provides them.
Water and Concentration
Water dissolves the dry alkali. The calculator offers three water methods. Lye concentration controls the strength of the solution. Water to lye ratio is common for simple planning. Water as a percent of oils is useful for older recipes. A stronger solution may trace faster. A weaker solution may take longer to unmold.
Superfat and Purity
Superfat reduces the alkali amount. It leaves extra unsaponified oils in the batch. Lye purity also matters. Potassium hydroxide often has lower purity than sodium hydroxide. Enter the purity shown on your container. This gives a more realistic amount to weigh.
Using the Result
The result shows oil weight, sodium amount, potassium amount, water, fragrance, additives, and batch yield. It also shows the final batch after estimated loss. Use the table as a planning guide. Always measure with an accurate scale. Wear gloves and eye protection. Mix lye into water, never water into lye. Test finished soap before use.
Record Keeping
Good records make repeat batches easier. Save the calculated report before you make changes. Note the room temperature, oil temperature, mold size, cure time, and final feel. Small notes help you improve the next recipe. They also help you compare different lye splits without guessing. Careful records support safer, cleaner, and more consistent soap making. They help beginners and experienced makers improve safely.
FAQs
What is a dual lye soap calculator?
It calculates recipes that use both sodium hydroxide and potassium hydroxide. The tool splits the alkali amount by your chosen ratio and adjusts it for superfat and purity.
Why use both NaOH and KOH?
NaOH helps build firmness. KOH can improve solubility and creamy lather. Together, they help create shave soap, hybrid bars, and specialty textures.
What does NaOH share mean?
NaOH share is the percent of the alkali plan assigned to sodium hydroxide. The remaining percent is assigned to potassium hydroxide automatically.
Why is KOH purity important?
KOH is often sold below perfect purity. If purity is lower, you need more actual KOH by weight to deliver the required active alkali.
Can I use custom oils?
Yes. Select custom oil and enter both NaOH and KOH SAP values. Use reliable supplier data when adding custom values.
Which water method should I use?
Lye concentration is best for precise planning. Water to lye ratio is simple. Water as a percent of oils is useful for older recipe styles.
Does this replace safety testing?
No. It is a planning tool. Always verify your recipe, use accurate scales, follow lye safety rules, and test finished soap before use.
Can I export the result?
Yes. After calculation, use the CSV or PDF buttons. The export includes the main result and oil breakdown for your records.