Stride length
Distance between two successive points of initial contact of the same foot. Distance covered when both feet have completed the full cycle of movement (one step with each foot)
Step length
Distance between the point of initial contact on one foot and the point of initial contact on the other foot. Measures how far one foot travels during a single step.
How to measure stride length
From initial contact of one foot to the initial contact of the same foot again. Includes both left and right feet.
How to measure step length
From heel strike of one foot to the heel strike of the other foot.