How to Measure Your Garage Door Opening for a Replacement Door

By Sky Houck, Owner — AZ Garage Door Repair · Updated May 5, 2026

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Why Accurate Measurements Matter

Ordering a garage door based on rough estimates leads to delays, returns, and additional costs. An accurate measurement ensures the door fits your opening correctly, the track system aligns properly, and the opener has adequate clearance. Whether you are getting quotes or ordering a door, you need five measurements: width, height, headroom, side room, and depth.

Measurement 1: Width of the Opening

Measure the width of the garage door opening at floor level — from the inside edge of the left jamb (the vertical framing member) to the inside edge of the right jamb. Measure in inches. Also measure the width at the halfway point and at the top of the opening. If the measurements differ, use the widest measurement. Standard residential widths are 96″ (8 feet), 108″ (9 feet), 120″ (10 feet), 192″ (16 feet), and 216″ (18 feet).

Measurement 2: Height of the Opening

Measure the height from the garage floor to the underside of the header (the horizontal framing member across the top of the opening). Measure on both the left and right sides. If the floor is uneven, use the shorter measurement. Standard heights are 84″ (7 feet), 96″ (8 feet), and 108″ (9 feet) for residential; 144″ (12 feet) to 192″ (16 feet) for RV garages.

Measurement 3: Headroom

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Headroom is the distance from the top of the door opening to the ceiling (or the lowest ceiling obstruction — beams, joists, lights, ductwork). Measure from the bottom of the header to the nearest obstruction directly above. You need:

Standard-lift installation: Minimum 12 inches of headroom.
Low-headroom installation: Minimum 3.5 to 6 inches (requires special low-headroom track hardware).
High-lift installation: Requires headroom equal to the standard 12 inches plus the additional lift height desired.

Insufficient headroom is the most common reason a door installation requires special hardware — always measure this accurately.

Measurement 4: Side Room

Side room is the distance from the edge of the door opening to the nearest side wall (or obstruction) on each side. Measure on both the left and right. Standard track installation requires a minimum of 3.75 inches of side room on each side for the vertical tracks. Low-clearance track options are available for tighter spaces.

Measurement 5: Depth (Backroom)

Depth is the distance from the opening to the back wall of the garage. When the door is fully open, it rests horizontally under the ceiling. The horizontal tracks must have enough room to accommodate the full length of the door plus the opener rail. For a 7-foot-tall door, you need at least 10 feet of depth. For an 8-foot-tall door, at least 11 feet.

Additional Notes

Floor levelness: Place a 4-foot level on the floor across the opening. Note any slope or unevenness — this affects the bottom seal fit and may require a floor threshold seal for a proper closure.
Existing tracks: If you are replacing a door on existing tracks, note the track radius (standard, low-headroom, or high-lift) and the track size.
Obstructions: Note the location of any lights, electrical outlets, pipes, shelving, or other items near the opening that might interfere with track installation.

Free Professional Measurement in Tucson

AZ Garage Door provides free on-site measurements for all replacement door quotes. We measure everything including headroom, side room, and depth to ensure your new door fits perfectly. Schedule your free measurement today. Learn more about our garage door repair services service.

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About the author: Sky Houck

Sky is the owner of AZ Garage Door Repair, a family-owned Tucson garage door company rated 5.0 stars across 100+ Google reviews. He still runs service calls across the Tucson metro, and every guide on this site is based on real jobs his crew handles every week.

Frequently Asked Questions

Common questions answered by AZ Garage Door Repair.

What does a garage door spring repair cost in Tucson?

AZ Garage Door Repair charges from $335 per spring plus labor. Final pricing depends on the spring tier you choose and is quoted up front before any work begins.

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Same-day service across Tucson and surrounding metro. Central Tucson calls reached in 60-90 minutes; Oro Valley, Marana, Foothills 90-120 minutes. 24/7 emergency dispatch — nights, weekends, and holidays included.

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AZ Garage Door Repair is bonded & insured with Bonded & Insured on every job. Our highly-trained technicians average 8+ years of field experience.

What brands does AZ Garage Door Repair install and service?

AZ Garage Door Repair is a Clopay supplier and LiftMaster supplier. We service all major brands including Genie, Wayne Dalton, Amarr, Chamberlain, Craftsman, and CHI.

What areas does AZ Garage Door Repair cover?

AZ Garage Door Repair serves Tucson, Oro Valley, Marana, Casas Adobes, Sahuarita, Catalina Foothills, Vail, SaddleBrooke, Tanque Verde, Rincon Valley, and the entire Pima County metro.