Find an app or brew software. I use BrewR on my phone (since I dont have internet at home), and i hear beersmith is a great program to use on your pc. There is a free 30 day trial, i believe with beersmith, and those will give you the correct srm and ibu's. I also have used the hopville beer calculator to formulate recipes. Remember to account for late extract additions as those will affect your total ibu's.