Running enthusiasts, next time you complete a 5K pat yourself on the back and say to yourself, "I just finished Super Mario Bros."
Extrapolating the distance of each level, assuming Mario's small size and his stride are those of an average man, Nick Greene of Mental Floss calculated that Mario runs 3.4 miles from world 1-1 to world 8-4 (so, about 5.4 kilometers.) This is a straight-line run on the solid ground portions, and doesn't account for things like backtracking, nor skipping ahead with bonus levels. Mario, obviously, ascends and descends, and stops and starts.
The water levels add another 371 meters, more than 7 laps in an Olympic pool. So after running a 5K Mario is basically jumping in for a 400 meter freestyle race. Too bad he doesn't bicycle any of these levels, then it could be a triathlon.
Speed Demos Archive, the hosts of the the Games Done Quick event taking place right now, lists the fastest, no-warp, all-stages time for Super Mario Bros. at 19 minutes, 40 seconds. So Mario's fast — running about a 5:30 mile pace. But not world class. His 5K time would be about 17:15, nearly 4 minutes and 22 seconds slower than the world record holder in the 5000 meters.