I guess at some point - there would be some max length to usb cable length due to the resistance of the wire - that length would vary with the gauge of the wire in the usb connector and ... who knows how to figure that out? lol. Even with a 'cheap' usb wire - the length would be considerable though. As a practical example, in my home theater, I use an external usb keyboard/touchpad. The length of the cable (using usb extensions) is about 40 feet. It works perfectly.