How many miles is one step?

Can you really equate the distance traveled in one step to a fixed number of miles? Isn't the length of a step highly dependent on factors such as the person's height, stride length, and even the surface they're walking on? Wouldn't it be more accurate to say that one step is a unit of measurement that can vary widely depending on individual characteristics and circumstances? So, my question is, how do we even begin to calculate the number of miles in one step without first accounting for all these variables?