To measure your inseam, stand upright with your back against a wall and your feet shoulder-width apart. Place a book or a similar object between your legs, with one edge against the wall and the other edge against your crotch (as if you were sitting on a bike saddle). Measure the distance from the top edge of the book to the floor. This is your inseam measurement. Make sure to take the measurement while wearing cycling shorts or similar clothing for accuracy.