In my opinion if you're creating your own soap recipes from scratch, and even if you're using a recipe from a book or website, it's VERY important to run your recipes through a lye calculator to make sure that your ratios of water, oils and lye are correct. By doing so will help insure that your batch of soap will come out just right. The one I use is the following link:
I love its diversity, it has endless kinds of oils that can be used. Once you use it for awhile I found that adjustments are simple. You can use ounces or grams. You can make alterations to your recipe and within seconds you can see the benefits or not, from the changes you have made.