Advanced Calculator
Example Data Table
| Oil | Weight | NaOH SAP | Recipe Role |
|---|---|---|---|
| Olive Oil | 500 g | 0.134 | Conditioning and mildness |
| Coconut Oil 76° | 250 g | 0.183 | Cleansing and lather |
| Palm Oil | 200 g | 0.142 | Hardness and stable bar structure |
| Castor Oil | 50 g | 0.128 | Bubbly lather support |
Formula Used
Base NaOH = oil weight × NaOH SAP value.
Discounted NaOH = base NaOH × (1 − superfat percentage).
NaOH to weigh = pure NaOH ÷ NaOH purity fraction.
KOH conversion = NaOH equivalent × 1.403 for potassium hydroxide.
Water by lye concentration = lye × ((100 − concentration) ÷ concentration).
Water by ratio = lye × selected water:lye ratio.
Water by oil percentage = total oils × selected water percentage.
Total batch weight = oils + alkali + water + fragrance + additives.
How To Use This Calculator
- Select the weight unit for the whole recipe.
- Add each oil and its weight.
- Use a custom SAP only when you know the exact value.
- Choose the alkali type and purity.
- Enter your preferred superfat percentage.
- Select a water method for your recipe style.
- Add fragrance, additives, cost, and mold details.
- Press calculate and review the result above the form.
- Download the CSV or PDF result for your records.
Cold Process Soap Planning Guide
Why Accurate Lye Matters
Cold process soap depends on careful measurement. Each oil needs a different lye amount. This is because every fat has its own saponification value. A small mistake can change the final bar. Too much lye can make soap harsh. Too little lye can leave excess oil. A good calculator reduces that risk.
Understanding Superfat
Superfat is the lye discount in the recipe. It leaves a controlled amount of unsaponified oil. Many makers use five percent for balanced bars. Higher superfat can feel richer. It may also reduce lather and shelf life. Lower superfat can feel cleaner. It needs more careful weighing.
Choosing Water Settings
Water affects trace, unmolding, and curing. Water as a percentage of oils is simple. Lye concentration gives more control. A higher concentration uses less water. It may trace faster. A lower concentration gives more working time. It may need a longer cure. The water:lye ratio is useful for repeat batches.
Balancing Oil Qualities
Each oil adds different qualities. Coconut oil raises cleansing and bubbles. Olive oil adds mild conditioning. Palm, tallow, butters, and similar fats improve hardness. Castor oil supports lather. The quality table gives a useful estimate. It does not replace testing. Real results also depend on fragrance, additives, cure time, and technique.
Batch Cost And Mold Fit
Cost fields help price each batch. Enter ingredient cost per selected weight unit. The calculator estimates total cost and cost per bar. Mold fields estimate a suggested oil weight. This helps match the recipe to the mold. Use the target oil weight to resize a recipe without changing oil percentages.
Safety Reminder
Always wear gloves, goggles, sleeves, and closed shoes. Mix lye into water. Never pour water into lye. Work with good ventilation. Check fragrance limits before use. Cure finished bars until they are mild, firm, and stable.
FAQs
1. What does this cold process soap calculator do?
It calculates oils, lye, water, fragrance, additives, batch weight, cost, and estimated soap qualities. It also supports superfat, lye purity, dual lye, and recipe resizing.
2. Can I use ounces instead of grams?
Yes. Select ounces from the unit field. Keep every weight and cost entry in the same selected unit for consistent results.
3. What is a SAP value?
A SAP value shows how much alkali is needed to saponify one weight unit of oil. Different oils have different SAP values.
4. What superfat percentage should I use?
Many cold process recipes use about five percent. Very low superfat needs precision. Very high superfat can soften bars and reduce shelf life.
5. Which water method is best?
Beginners often use water as a percentage of oils. Experienced makers may prefer lye concentration because it gives more predictable water control.
6. Can this calculator handle dual lye recipes?
Yes. Choose dual lye and set the NaOH share. The remaining share is calculated as KOH using a standard conversion factor.
7. Is the mold estimate exact?
No. It is an estimate based on mold volume, fill level, and density. Test your mold and adjust the target oil weight if needed.
8. Does this replace soap safety testing?
No. It helps planning, but you should still verify SAP values, weigh carefully, follow lye safety, and test finished soap after curing.