Garage Door Size Calculator

How Garage Door Sizing Works

Choosing the right garage door size depends on your vehicle dimensions, available headroom, side room, and backroom. Undersizing causes clearance problems; oversizing wastes wall space and costs more.

Standard sizes:

Width calculation:

Minimum door width = Vehicle width + 6 inches (each side clearance)

A standard pickup truck is 79 inches wide. Add 12 inches total:

79 + 12 = 91 inches, which rounds up to a 9 ft door

That is the bare minimum, and it is not what this calculator recommends. Six inches a side clears the mirrors and nothing else: you still have to open the car door, and on a 9 ft opening with a truck centred in it there are 10 inches to play with on each side. The calculator recommends 10 ft for an SUV or pickup for exactly that reason, which is a foot wider than the code minimum and the size most people wish they had specified. Take the 9 ft figure as the number below which the door will not work at all, and the 10 ft figure as the one you will be happy with.

Height calculation:

Most cars clear a 7 ft door easily. Add clearance for:

• SUVs and trucks: use 8 ft minimum
• Cargo vans / campers: use 9–10 ft
• Lifted trucks: measure from ground to highest fixed point + 6 inches

Required headroom (above door opening):

• Standard torsion spring system: 12 inches minimum
• Low-headroom brackets: as little as 4.5 inches (specialty hardware)

Required side room:

• Standard: 3.75 inches each side
• Insulated doors: may need up to 5.5 inches

Required backroom (depth behind door when open):

Backroom = Door height + 18 inches (for opener travel)

An 8 ft tall door needs at least 9.5 ft of backroom depth behind the opening. That is measured from the inside face of the header straight back, and it has to be clear: no shelving, no water heater, no storage platform in the way of the track and the opener rail.

Always measure your widest vehicle before ordering. The door is permanent and the vehicle is not.