The height of your garage door directly impacts the purchasing decision of a garage door opener. Well, in some cases, you are also required to buy an extension kit. Mostly, an average garage door opener can handle the door of height approx. 7-foot-high and without modification. And, extension kits are necessary in case of taller doors. You have to pay extra for that. In general, garage door opener height is the distance from the floor to the garage's top door opening. So, other common factors also come into places such as side room, depth, headroom, and the highest point of travel, etc.