As of 20 August 2008, Usain Bolt is the the world's fastest man with a 200 meter sprint of 19.30 seconds, giving an average speed of 10.36 meters per second. There are 1609.344 meters in a mile, so 10.36 m/s / 1609.344 m/mi = 0.0064374 miles/second. There are 3600 seconds in an hour, so 0.0064374 mi/s * 3600 s/hr = 23.175 miles/hour. Usain Bolt clocked an *average* speed of 23.175 mph during his world record run, however he may have achieved speeds of 23-27 mph in the early part of the sprint.