Garage Door Opening Size Calculator
Calculate the recommended rough opening size for a garage door based on your vehicle dimensions and required clearances.
Typical car: 70–80 in, SUV/truck: 78–96 in
Typical car: 55–65 in, SUV/truck: 65–80 in
Minimum recommended: 3 in per side
Minimum recommended: 2 in above vehicle
Space between vehicles in multi-car openings
Formulas Used
Minimum Opening Width (in):
(Vehicle Width × Number of Cars) + (2 × Side Clearance) + ((Number of Cars − 1) × Between-Car Clearance)
Minimum Opening Height (in):
Vehicle Height + Top Clearance
Recommended Door Size:
Round up to the nearest standard door width (8, 9, 10, 12, 14, 16, 18, 20 ft) and height (7 or 8 ft).
Rough Opening:
Door Width + 3 in (framing) × Door Height + 1.5 in (framing)
Assumptions & References
- Minimum side clearance of 3 inches per side is recommended by the International Residential Code (IRC) and most door manufacturers.
- Minimum top clearance of 2 inches is required for most torsion spring and track hardware installations.
- Standard residential door widths: 8, 9, 10, 12, 14, 16, 18, 20 ft; standard heights: 7 ft and 8 ft.
- Rough opening adds 3 inches to width and 1.5 inches to height for framing and shimming per standard construction practice.
- Between-car clearance of 4 inches is a common minimum for multi-car openings to allow door opening without contact.
- Vehicle dimensions should be measured at the widest and tallest points including mirrors and roof racks.
- References: IRC Section R302, Wayne Dalton & Clopay installation guidelines, DASMA (Door & Access Systems Manufacturers Association).