What is 100% of power for a forehand or a backhand? Babolat 12 April 2018 11:15 Updated Follow 100% of power is almost equivalent to 220 km/h (75 mph). If you want to know why the PLAY racket cannot give an exact ball speed, click here . Related articles Why do we only have a percentage of power, and not a ball speed (in km/h or mph) for the forehands and backhands? Comments 0 comments Article is closed for comments.