How to size garage doors
Rough opening vs. finished size
Garage door rough opening is the same width as the door size; height adds 1–1.5″ to the door height for the header. Sectional doors need head room (12–18″ above the opening for the spring system) and back room (door height + 18″ behind the opening for the door tracks).
Standard sizes by use
Standard sizes: single-car 8–9″×7″ (9″×7″ is the modern default), double-car 16″×7″ (the most common new-construction size). RV doors are 8–9″ tall. Match the opening to the largest vehicle you actually plan to park: a 16″ double door fits two mid-size cars or one full-size pickup with mirrors folded.
Code and egress
Bedrooms must have an egress window or door (size, sill height, and operability vary by jurisdiction). For doors, check the rough opening, the door's swing direction, and the trim allowance before ordering.
Common mistakes
- Confusing nominal and rough-opening dimensions; they differ by 2–2.5″ for most pre-hung doors.
- Forgetting handle and lock side — this affects which way the unit must be ordered.
- Skipping the egress check on a bedroom remodel.