How to measure for a new garage door

Before you choose a new garage door, it helps to know the five measurements that matter: width, height, headroom, side room and backroom. This guide explains them as planning figures. Final measuring follows the chosen door's manufacturer instructions and is confirmed by the installer.

Measuring does not require touching the door's moving parts. Do not climb on the door, the tracks, the springs or the opener to measure, and do not reach into the spring area. Use a tape from the floor or a stable step ladder away from the door, and stay clear if the door is damaged or off its track. A damaged door should be inspected by a technician before anyone works around it.

Garage door manufacturers use the same five measurements. The numbers differ by maker and by track type, so the figures in this guide are examples, not rules.

Notice the headroom figures do not agree. That is the point. The right minimum depends on the track, the spring type and whether an opener is installed, so the maker of the door you pick sets the requirement.

1. Clear the area around the opening so nothing blocks the tape.
2. Measure the width of the opening between the inside jambs, and write it down in feet and inches.
3. Measure the height from the floor to the bottom of the header at the left, center and right. Record all three.
4. Measure headroom from the top of the opening up to the ceiling or the first obstruction, such as a pipe, light, beam or ductwork. Look along the whole width of the door.
5. Measure side room on the left and right, from the edge of the opening to the nearest wall or obstruction.
6. Measure backroom from the opening to the back wall or the first obstruction, such as a stored item you cannot move, a ceiling beam or a light fixture.
7. Photograph the opening, the ceiling above it and the sides, and write down any obstructions.

Clopay says the rough opening should match the door size and excludes stop molding. If the jambs are out of square, or the header is sloped, tell the installer.

• Track type. If headroom is tight, low-headroom track exists. Clopay's guide lists low-headroom tracks needing about 9 inches in front-mount and 4.5 inches in rear-mount forms, with more side room and backroom. Garaga lists dual-track low-headroom systems between 4-3/4 and 12 inches for torsion. Figures vary by maker.
• Spring type. Clopay says the side room available determines whether extension or torsion springs can be installed.
• Opener location. Springs and the opener both need dedicated space above the door.
• Door size. Common sizes are 8 or 9 feet wide for a single door, and 16 or 18 feet for a double door, with heights of 7 or 8 feet. Custom sizes exist.

DASMA says replacement doors should not be fitted to old track, because the track must suit the door's section thickness, weight, headroom and opener location. Plan on the track being part of the new door. See single vs double garage doors and headroom basics.

Overhead Door notes that a measurement from an online guide is only an initial one, and that unsure owners should have an on-site measurement. Clopay says a dealer can measure the opening, especially for non-standard or unusual openings. Our installers confirm the final measurements for the door you choose and take the actual opening, track and clearance into account.

• Sloped floors, out-of-square jambs or a sagging header.
• Obstructions in the headroom, such as an opener rail from an old door, a light, a pipe or a beam.
• A tight ceiling that needs low-headroom track.
• Wide or tall openings, or non-standard sizes.
• Side room under the manufacturer's minimum.

Stop and bring in a technician before measuring if the current door is damaged. Do not measure in a way that puts you near the moving door or its hardware.

• The door is crooked, off its track, stuck, or has a broken spring or cable.
• You have to reach into the spring area, near the springs, cables or bottom brackets, to take a measurement.
• You are thinking of removing the old door yourself. The old door is heavy and held up by springs under dangerous tension.

Springs, cables and brackets hold dangerous tension, and taking down an old door is technician work. Our technicians handle new garage door installation. For what happens on installation day, see what happens during a new garage door installation. For help choosing, read garage door materials compared and insulated vs non-insulated garage doors.

• New Garage Door Installation

• Amarr: How to measure for a new garage door
• Overhead Door: How to measure for a garage door
• Clopay: What are standard garage door sizes
• Clopay: Garage door track options, headroom and specs
• Garaga: Headroom required for a residential garage door
• DASMA: Garage door safety