Calculating Asteroid Impacts

I was reading this news item about the chances of a large meteorite striking the earth being more likely than previously thought. One of the comments directed me to Purdue's University's Asteroid Impact Calculator. Kinda hard to figure out what criteria to add to the formula, but still fun (and scary) to play with.

For what it's worth, the last one I tried was a 3 meter wide asteroid. According to the calculator most of it would burn up in the atmosphere.