Your standard commercial treadmills average 10-12 mph depending on the model and price. Some options are available at 15-16 mph but looking for anything even faster, you enter the non mainstream treadmills catergory designed for professional runners and athletes and max at roughly 18mph. If you are looking for treadmills with 4.0 hp motors, these offer a speed up to 28 mph, and are explicitly designed for world-class athletes.