Soap calculator for bar and liquid soap
Work out the lye (NaOH or KOH), water and fragrance for any soap recipe, and see the soap's properties before you make it. The database holds 148 oils, fats, butters and waxes with SAP values, iodine values and fatty-acid profiles. A free tool from Al-Maraseel in Mosul, Iraq.
1Settings
2Oils and percentages
Oils and percentages
| Oil | % | g |
|---|
Target ranges
Finds percentages that keep the properties inside the target ranges. Lock an oil to keep its percentage.
Caustic soda is corrosive: wear gloves and eye protection, add the lye to the water (never the reverse), and work in a ventilated area away from children.
How to use the calculator
- Choose the lye: sodium hydroxide (NaOH) for bar soap or potassium hydroxide (KOH) for liquid soap, and enter its purity.
- Enter the total oil weight, superfat, water and fragrance.
- Add oils from the list and set each percentage so they total 100%, or press “Suggest the best blend” to let the calculator choose.
- Read the results: lye, water and fragrance weights, and the soap properties against their target ranges.
What the soap properties mean
- Hardness
- How hard and long-lasting the bar is. Comes from the saturated acids: lauric, myristic, palmitic and stearic.
- Cleansing
- How strongly the soap strips oils. Comes from lauric and myristic acids (coconut and palm kernel oil); too high feels harsh on skin.
- Conditioning
- Comes from the unsaturated acids: oleic, linoleic, linolenic and ricinoleic, as in olive oil.
- Bubbly and creamy lather
- Big bubbles come from lauric, myristic and ricinoleic (castor oil); stable creamy lather from palmitic and stearic.
- Iodine and INS
- Iodine measures unsaturation: the higher it is, the softer the bar and the sooner it goes rancid. INS combines hardness and stability in one number; 136 to 165 is the usual target.
Frequently asked questions
How much caustic soda do I need per kilo of oil?
It depends on the oil: olive oil needs about 129 g of pure NaOH per kilo and coconut oil about 175 g, before the superfat discount. That is why the calculator works it out from each oil's own SAP value.
What is the difference between NaOH and KOH?
Sodium hydroxide (NaOH) makes hard bar soap; potassium hydroxide (KOH) makes soft or liquid soap. You need about 1.4 times more KOH than NaOH by weight for the same oil.
What superfat should I use?
3% to 8% is common. A higher superfat gives a milder but softer bar that goes rancid sooner. 5% is a good start for most recipes.
How accurate is the calculator?
It uses published SAP values for each oil. Real oils vary a little with source and processing, which is what the superfat allows for. Test a new recipe in a small batch first.