No it's not really that wierd. Each oil we use has a range for SAP values. Each calc is using a number in that range, not necessarily the same number. I use 2 different soap calcs. I use the one from MMS when I have a recipe with ounces. http://thesage.com/calcs/lyecalc2.php When I only have a recipe with percentages I use the soapcalc. http://www.soapcalc.com/calc/SoapCalc.asp I also like that you can save the soapcalc on your computer to use offline. Click on file, save as, and then I saved it on my desktop so I can always find it.