Soap Calculator
Build a balanced recipe with classic oils, lye, and water ratios.
1. Type of Lye ?
Choose what kind of lye you will be using.
Sodium hydroxide, NaOH, is used to make soap bars. If you want to make bar soap, click the circle next to NaOH.
Potassium hyroxide, KOH, is used to make liquid soap. This is a more complicated process than making bar soap. It involves adding the water in two stages: one for the soap cooking stage, the other for diluting the soap. You can find more about it here. When making liquid soap, click the circle next to KOH. If you have 90% pure KOH check the 90% box.
Choose what kind of lye you will be using.
Sodium hydroxide, NaOH, is used to make soap bars. If you want to make bar soap, click the circle next to NaOH.
Potassium hyroxide, KOH, is used to make liquid soap. This is a more complicated process than making bar soap. It involves adding the water in two stages: one for the soap cooking stage, the other for diluting the soap. You can find more about it here. When making liquid soap, click the circle next to KOH. If you have 90% pure KOH check the 90% box.
2. Weight of Oils ?
This value is the total weight of all the oils that will be used in your recipe. You can use either pounds, ounces or grams as your unit of measurement.
No matter what unit of measurement you use to create your recipe, the calculated values are displayed in pounds, ounces and grams after clicking the 'View/Print Recipe' button.
This value is the total weight of all the oils that will be used in your recipe. You can use either pounds, ounces or grams as your unit of measurement.
No matter what unit of measurement you use to create your recipe, the calculated values are displayed in pounds, ounces and grams after clicking the 'View/Print Recipe' button.
3. Water ?
'Water as % of Oils' is the simplest way to determine the amount of water used in your recipe. It is recommended that beginners use this method and use the default value of 38%.
More experienced users typically reduce this percentage to around 32-33%.
Example: Using the default 38% and the total weight of the oils in your recipe is 1 pound, the amount of water in which the lye is mixed would be 0.38 pounds. The water and lye amounts are calculated on the 'View Recipe' page.
'Lye Concentration' - Advanced users can set the Lye percentage of the water & lye solution directly. Example: If you want lye to be 34% of (lye + water), click 'Lye Concentration' and enter 34 in the text box to the right of the check box before clicking 'Calculate Recipe'.
'Water : Lye Ratio' - Advanced users can also set the Water:Lye ratio directly. Example: If you want the water to lye ratio to be 2 to 1, click 'Water : Lye Ratio' and enter 2:1 before clicking 'Calculate Recipe'.
'Water as % of Oils' is the simplest way to determine the amount of water used in your recipe. It is recommended that beginners use this method and use the default value of 38%.
More experienced users typically reduce this percentage to around 32-33%.
Example: Using the default 38% and the total weight of the oils in your recipe is 1 pound, the amount of water in which the lye is mixed would be 0.38 pounds. The water and lye amounts are calculated on the 'View Recipe' page.
'Lye Concentration' - Advanced users can set the Lye percentage of the water & lye solution directly. Example: If you want lye to be 34% of (lye + water), click 'Lye Concentration' and enter 34 in the text box to the right of the check box before clicking 'Calculate Recipe'.
'Water : Lye Ratio' - Advanced users can also set the Water:Lye ratio directly. Example: If you want the water to lye ratio to be 2 to 1, click 'Water : Lye Ratio' and enter 2:1 before clicking 'Calculate Recipe'.
4. Additional Settings ?
Super Fat. Due to several possible oil variables it is safer to use less lye than needed to saponify the oils in your recipe. This is called a lye discount and 5% is generally considered a safe number to use.
Because discounting the lye by 5% leaves 5% of unsaponified oils in your soap bar this number is also referred to as super fat. That extra 5% of superfat not only is a safety factor, it also gives the soap bar extra skin conditioning qualities because approximately 95% of the bar is soap and approximately 5% of the bar is an oil mixture that is deposited on the skin. For more info see FAQ Number 7
Fragrance. The amount of fragrance to use is typically about 3-4% of the total weight of the oils used in your recipe. This is commonly specified as ounces per pound of oils or grams per kilogram of oils. Some suppliers will specify a usage rate for each of their oils.
Example: The supplier suggests a usage rate .6 oz/lb: 0.6/16 oz = .0375 = 3.75%. The metric equivalent would be .0375 x 1000 = 37.5 g/kg. Essential Oils are stronger and usually require a lower percentage than Fragrance Oils.
Super Fat. Due to several possible oil variables it is safer to use less lye than needed to saponify the oils in your recipe. This is called a lye discount and 5% is generally considered a safe number to use.
Because discounting the lye by 5% leaves 5% of unsaponified oils in your soap bar this number is also referred to as super fat. That extra 5% of superfat not only is a safety factor, it also gives the soap bar extra skin conditioning qualities because approximately 95% of the bar is soap and approximately 5% of the bar is an oil mixture that is deposited on the skin. For more info see FAQ Number 7
Fragrance. The amount of fragrance to use is typically about 3-4% of the total weight of the oils used in your recipe. This is commonly specified as ounces per pound of oils or grams per kilogram of oils. Some suppliers will specify a usage rate for each of their oils.
Example: The supplier suggests a usage rate .6 oz/lb: 0.6/16 oz = .0375 = 3.75%. The metric equivalent would be .0375 x 1000 = 37.5 g/kg. Essential Oils are stronger and usually require a lower percentage than Fragrance Oils.
5. Select Oils, Fats, and Waxes ?
When one oil is selected from the list (Oils, Fats and Waxes) the values in the 'One' column will change and be specific for the selected oil. The SAP values will change and the name of the oil will be highlighted or displayed under 'Oils, Fats and Waxes'. Go ahead, select an oil to see the change.
After you have entered the oils for your recipe and 'Calculate Recipe' is clicked the righthand 'All' column displays the values for your recipe. The next Help #6 explains how to add an oil to the recipe list.
There are 7 Soap Qualities and 8 Fatty Acids listed.
To Pop up more...
- PC - mouse over the word.
- Tablet - tap the word.
To close the pop up:
- iPad - tap any text box just to the right of the words.
- Android - Tap the popup to close it OR tap any text box just to the right of the words.
At the bottom of this column the ratio of saturated to unsaturated fats is displayed after clicking 'Calculate Recipe'. A typical ratio would be around 40:60 although there are many exceptions to this guideline.
To learn more about fatty acids in general, click on the 'Fatty Acids' link to Wikipedia at the top of this section.
To go to the Wikipedia page for a specific fatty acid click on the 'i' button to the right of its name.
When one oil is selected from the list (Oils, Fats and Waxes) the values in the 'One' column will change and be specific for the selected oil. The SAP values will change and the name of the oil will be highlighted or displayed under 'Oils, Fats and Waxes'. Go ahead, select an oil to see the change.
After you have entered the oils for your recipe and 'Calculate Recipe' is clicked the righthand 'All' column displays the values for your recipe. The next Help #6 explains how to add an oil to the recipe list.
There are 7 Soap Qualities and 8 Fatty Acids listed.
To Pop up more...
- PC - mouse over the word.
- Tablet - tap the word.
To close the pop up:
- iPad - tap any text box just to the right of the words.
- Android - Tap the popup to close it OR tap any text box just to the right of the words.
At the bottom of this column the ratio of saturated to unsaturated fats is displayed after clicking 'Calculate Recipe'. A typical ratio would be around 40:60 although there are many exceptions to this guideline.
To learn more about fatty acids in general, click on the 'Fatty Acids' link to Wikipedia at the top of this section.
To go to the Wikipedia page for a specific fatty acid click on the 'i' button to the right of its name.
| One | All | |
|---|---|---|
| Hardness | 6 | 0 |
| Cleansing | 0 | 0 |
| Conditioning | 94 | 0 |
| Bubbly | 0 | 0 |
| Creamy | 80 | 0 |
| Iodine | 98 | 0 |
| INS | 70 | 0 |
| Lauric | 0 | 0 |
| Myristic | 0 | 0 |
| Palmitic | 3 | 0 |
| Stearic | 2 | 0 |
| Ricinoleic | 0 | 0 |
| Oleic | 18 | 0 |
| Linoleic | 11 | 0 |
| Linolenic | 4 | 0 |
| KOH SAP | 0.168 |
| NaOH SAP | 0.120 |
| Sat : Unsat | No Data |
6. Recipe Oil List ?
To add an oil to your recipe:
- PC - select it from the list in the middle and double click it or click the '+' in the 'Soap Recipe' section just to the right of the oil list.
- Tablets - press the selection box just under 'Oils, Fats and Waxes', make the oil selection, then press the 'Add' button just below 'Recipe Oil List'' OR press the '+' sign by the appropriate oil number.
To remove an oil from your recipe:
- PC or Tablets - click the '-' next to the oil you want to remove OR Enter the recipe number (1-14) in the text box next to the button 'Remove #', then press the Remove button.
To add an oil to your recipe:
- PC - select it from the list in the middle and double click it or click the '+' in the 'Soap Recipe' section just to the right of the oil list.
- Tablets - press the selection box just under 'Oils, Fats and Waxes', make the oil selection, then press the 'Add' button just below 'Recipe Oil List'' OR press the '+' sign by the appropriate oil number.
To remove an oil from your recipe:
- PC or Tablets - click the '-' next to the oil you want to remove OR Enter the recipe number (1-14) in the text box next to the button 'Remove #', then press the Remove button.
| Action | Oil Name | % | Weight (lb) |
|---|---|---|---|
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| 14. | |||
| Totals | 0.00% | 0.000lb |
Please add at least one oil to your recipe.
About This Calculator
SoapCalc calculates exact lye and water amounts for your soap recipe based on the specific oils you're using. Each oil has a different saponification (SAP) value — the amount of lye needed to turn that oil into soap. Get the lye wrong and you end up with soap that's either caustic or a greasy mess. The calculator removes that guesswork.
It works for cold process, hot process, and liquid soap. Choose NaOH (sodium hydroxide) for bar soap or KOH (potassium hydroxide) for liquid soap — or use both for dual-lye recipes. The oil database includes over 150 oils, fats, butters, and waxes, each with SAP values, fatty acid profiles, and soap quality predictions.
As you build your recipe, the soap qualities update in real time: hardness, cleansing, conditioning, bubbly lather, and creamy lather. You can see how your recipe will perform before you make the batch. Adjust an oil percentage, swap one fat for another, change your superfat — the numbers recalculate instantly.
When you're done, click View Recipe Summary for exact lye, water, and oil weights in pounds, ounces, and grams. Print it, export it as a JSON file, or jot it down in your soap notebook and head to the kitchen.
New to Soap Making?
If this is your first time using a soap calculator, start with our step-by-step tutorial — it walks through every field in the calculator and explains what each setting means. The getting started guide covers the basics of cold process, hot process, and melt and pour soap making, including a simple three-oil beginner recipe you can run through this calculator right now.
For questions about superfat, lye concentration, water percentages, and how to read the soap quality numbers, check the FAQ and the soap qualities page. And if you want to compare oils before adding them to your recipe, the sortable oil chart shows SAP values, fatty acid breakdowns, and properties for every oil in the database.
Need help from other soap makers? The soap making community page has links to active forums, Facebook groups, and other resources.