Door Rough Opening Calculator
When framing a wall for a door, the rough opening must be larger than the door itself to allow room for the door frame (jambs), shims, and installation tolerances. The standard practice for pre-hung interior and exterior doors is to frame the rough opening 2 inches wider and 2 inches taller than the door slab size. For example, a standard 2-8 (32-inch) door that is 80 inches tall requires a rough opening of 34 inches wide and 82 inches tall. This allows space for the jamb (typically 3/4 inch on each side), plus shimming room of about 1/4 inch on each side. The rough opening height accommodates the jamb, the sill (or threshold on exterior doors), and a small gap at the top. Always verify the rough opening requirements with the specific door unit manufacturer, as some pre-hung units specify slightly different dimensions. This calculator provides the standard industry framing dimensions and also shows the header length (rough opening width plus any bearing length) for quick lumber ordering reference.
Door rough opening formula
RO Width = Door width (in) + (2 x Width clearance per side)
RO Height = Door height (in) + Height clearance
Worked example
Door: 32 in wide x 80 in tall. Standard clearance: 1 in each side, 2 in total height.
- RO Width = 32 + (2 x 1) = 34 inches (2 ft 10 in)
- RO Height = 80 + 2 = 82 inches (6 ft 10 in)
Common door sizes and rough openings
| Door size | RO Width | RO Height (80 in door) |
|---|---|---|
| 2-0 (24 in) | 26 in | 82 in |
| 2-4 (28 in) | 30 in | 82 in |
| 2-6 (30 in) | 32 in | 82 in |
| 2-8 (32 in) | 34 in | 82 in |
| 3-0 (36 in) | 38 in | 82 in |
Frequently asked questions
How much bigger is the rough opening than the door?
The standard rough opening is 2 inches wider and 2 to 2.5 inches taller than the door size. This allows room for the door frame (jambs and sill), shims for leveling and plumbing, and clearance for proper operation. For pre-hung doors, the rough opening is typically door width + 2 inches wide and door height + 2 inches tall.
What is the rough opening for a 32-inch door?
A 32-inch wide door (2-8 in trade sizing) requires a rough opening of 34 inches wide (32 + 2) and 82 inches tall for a standard 80-inch (6-8) door (80 + 2). This accommodates a pre-hung door unit with jambs, shims, and the door slab.
Do I need a header above the door rough opening?
Yes. In load-bearing walls, a structural header spanning the rough opening is required to transfer loads around the opening to the jack studs (trimmers) and king studs on either side. Header size depends on the span and load. Consult your local building code or the American Wood Council's span tables.
What are jack studs and king studs?
King studs are full-height studs on either side of a rough opening that run from the bottom plate to the top plate. Jack studs (also called trimmer studs) are shorter studs installed inside the king studs that support the header. Together they form the rough opening frame.
Is the rough opening different for exterior versus interior doors?
The rough opening calculation is the same for both. However, exterior door frames and sills are typically thicker to accommodate weatherproofing and flashing, so verify the specific door unit dimensions with the manufacturer. Pre-hung units include installation instructions specifying the required rough opening.
Sources
- Door and Access Systems Manufacturers Association (DASMA): door framing standards.
- International Residential Code (IRC): Section R602 Wall framing and openings.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. Always verify rough opening with the door manufacturer's installation instructions.