This is a list of saponification values for a number of common fats used in making soap and how much alkali you need, I can’t guarantee they are 100% accurate and you should always use around 2-5% less alkali to account for natural variation in the fats at least for your first attempt, if the end result is too alkaline use even less alkali, if your soap feels too fatty, fails to lather or the PH is less than around 8 you will need more.
Higher saponification values usually make better soaps, however some can contain a significant amount of of unwanted materials that make them more undesirable, lard for example, I have not included these here although you may be able to purify these fats with more work.
The ideal PH depends on the intended purpose and your skin, 8-9 is good for sensitive or dry skin, 9-10 is about average, 10-11 is a harsh soap good for removing significant amounts of grease and oil, 12 or above will likely result in your skin falling off so it should only be used with gloves, keep in mind higher PH soaps tend to lather better without needing additional additives, with liquid soaps you have the option of adjusting the PH later.
How to use
Firstly weigh out your fat / oil with some digital scales, if you are using more than one fat you will need to calculate the amount of alkali needed for each fat then add them all up, once that is done you may want to reduce the final value by about 2-5% if this is your first time using a particular fat or mixture of, small batches are recommended at first before you scale up.
Saponification Values
| Fat | Saponification Value | g NaOH/g | g KOH/g |
| Beef Tallow | 196 | 0.14 | 0.196 |
| Canola Oil | 173 | 0.123 | 0.173 |
| Cocoa Butter | 188-200 | 0.138 | 0.194 |
| Coconut Oil | 250-265 | 0.184 | 0.258 |
| Corn Oil | 190 | 0.135 | 0.19 |
| Hemp Seed Oil | 190-195 | 0.138 | 0.193 |
| Olive Oil | 184-196 | 0.135 | 0.19 |
| Palm Oil | 190-205 | 0.141 | 0.198 |
| Rapeseed Oil | 175 | 0.125 | 0.175 |
| Shea Butter | 170-190 | 0.128 | 0.18 |
| Soybean Oil | 180-200 | 0.135 | 0.19 |
| Sunflower Oil (High Oleic) | 191 | 0.136 | 0.191 |
Note that the amount of alkali is grams per gram of fat.
Example
If you wanted to make a soap using 500g of total fat, containing 70% olive oil and 30% coconut oil using sodium hydroxide.
First calculate how much olive and coconut oil you need:
$$olive = 500g * 0.7 = 350g$$
$$coconut = 500g * 0.3 = 150g$$
Next calculate the amount of sodium hydroxide you need for each:
$$olive = 350g * 0.135g = 47.25g$$
$$coconut = 150g * 0.184g = 27.6g$$
Then add them up for the total amount of NaOH:
$$NaOH = 47.25g + 27.6g = 74.85g$$
Then to be extra safe we will reduce this by 2%
$$NaOH = 74.85g – (74.85g * 0.02) = 73.35g$$
Make it then adjust as needed if the PH is not correct.