SoapCalc.com
This is my favorite soap calculators. I use this in conjunction with Soapmaker Software. One great thing about Soap Calc is the “Soap Qualities” column on the left side. It’s a great indicator of what your soap properties will be in it’s final stage. Never get too hung up on the numbers though as no calc is perfect!

Soapmaker Software
This is a great program. I can formulate recipes in it of course but it has so much more to offer than that. For starters I can enter and store the specific gravity of my particular oils if my supplier can provide them for me. It also calculates my cost per batch and per bar using the $$ amounts I entered after purchasing supplies. Another great feature is that it tracks inventory-both supplies and product. Best of all, it stores every recipe I have ever tried. With notes. While I prefer to formulate my recipes in Soap Calc, I can’t live without the features provided in this program.

Summer Bee Meadow
Liquid soapmakers are particularly fond of this calc, but it’s great for bar soap too! You can also use their Recipe Resizer to fit your mold, rectangular or round.

Miller Soap Recipe Spreadsheets
Miller Soap has a collection of Microsoft Excel spreadsheets to use to create your own recipes. These are a nice way to formulate and save your recipes locally. And they’re free!

Majestic Mountain Sage Lye Calculator
One of the very first online lye calculators and a very popular one too.

RJ’s Soap List Lye Calculator
RJ’s Calculator allows for water discounts to be entered into the recipe at the top. It’s great for soapers that discount water regularly.

Snowdrift Farm Soap Calculator
Allows you to enter negative lye discounts for the liquid soap formulas making it great for liquid and bar soap users.