I tend to like to over estimate my calorie intake (Over estimate calories under estimate Exercise), so I don't factor in the drained part. And when you say drained I am assuming you are talking about drained of grease, because ground beef can have varying degrees of filler which is where some of the extra fat comes from. So extra lean usually has 91% beef and 9% filler, all the way to one I saw that was 70% beef and 30% filler. So that is something I feel is more important to know then just draining the grease.

Side note: I used to have one of those old timey meat grinders (it gets really messy if the grinder isn't over a bucket), at that point I would calculate the calories to be the tip of meat/cut that I put into the grinder. Not sure if you are grinding your own sirloin but thought I would throw it out there.