I didn't read all of these responses, so forgive me if I'm repeating some things. But my friend actually works in the athletic department as a sort of expert on these very things. He does all the testing on the athletes to get there stats Vo2 max, max HR, body fat, etc.

The calculation that is typically used is 220 - your age. That is a VERY generic calculation. The only way to truly determine your Max HR is to go to an expert and literally push yourself to that point. Don't do this on your own, it can be dangerous and it's extremely uncomfortable! According to that calculation, my Max HR is 188. I know for a fact that it's higher as I can hit 188 and feel fine, if tired. I had mine tested by my friend 2 years ago and it was 199. I'd hazard to guess it's about the same now as I still exercise and peak the same way. My ex has a crazy high Max HR. In fact. At my age (32), it was reaching 203 at it's peak regularly. We ended up going to a doctor and having an EKG to make sure nothing was wrong. Everything was fine.

People are just different. My resting HR is usually about 48. When I'm extremely relaxed, it's gone down as low as 42. But when I work out, it's usually higher than everybody else. It's just the way my body works. There is no "calculation" that can accurately assess this.