 From his record time of 9 @.@ 58 s for the 100 m sprint , Usain Bolt 's average ground speed equates to 37 @.@ 58 km / h ( 23 @.@ 35 mph ) . However , once his reaction time of 0 @.@ 15 s is subtracted , his time is closer to 9 @.@ 43 s , making his average speed closer to 38 @.@ 18 km / h ( 23 @.@ 72 mph ) . Bolt 's top speed , based on his split time of 1 @.@ 61 s for the 20 metres from the 60- to 80 @-@ metre marks ( made during the 9 @.@ 58 WR at 100m ) , is 12 @.@ 42 m / s ( 44 @.@ 72 km / h ( 27 @.@ 79 mph ) ) . 
