Understanding your result
The headline is the rough opening, width × height, and the line under it repeats the door or window size it is for. The tiles give the header length, the king and jack studs, and the cripples. The table gives each piece of the opening’s framing with its length.
Width and height each show their arithmetic: the unit size plus the clearance used. For a pocket door the width is twice the door plus an inch, because the opening includes the pocket. The jack studs are cut to the opening height (plus the space below a window); the king studs run the full height of the wall; the cripples fill the space above the header, and below a window sill, at the stud spacing so the drywall has a fastening surface.
The header is the rough opening plus two jack studs. Its size is the one thing this page will not decide for a wall that carries load. For the studs of the whole wall around the opening, use the wall stud calculator; for the whole wall with its board, the partition wall calculator; for backing next to the door for a heavy door stop or a coat rack, the blocking calculator.
How we calculate this
The clearances are the common published rules of thumb for each product type; the table states the source each time. The cripple length assumes a header 3-1/2 in deep (a 2 × 4 on edge, or two flat 2 × 4s) and a wall with one bottom and two top plates; a 97-1/8 in wall built from 92-5/8 in precuts is the default. Standard door, window and opening sizes are on the standard sizes table.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Pre-hung interior door | Slab + 2 in wide, + 2-1/2 in high | Common pre-hung door practice and door makers’ sheets |
| Window | Unit + 1/2 in each way | Window makers’ installation instructions |
| Pocket door frame | 2 × door + 1 in wide, + 4-1/2 in high | Pocket door frame kit instructions |
| Header in a non-bearing wall | Flat or doubled 2 × 4, opening + 3 in | Common framing practice |
| Header in a bearing wall | Not covered | IRC R602.7 span tables |
| Wall height | 97-1/8 in | 92-5/8 in precut + three plates |
Assumptions last reviewed October 8, 2026.
The calculator does not size headers for load, does not handle double doors, bifolds or barn doors (whose hardware sets the opening), and does not account for door frames in steel walls, where the opening is framed with track. The maker’s sheet for your door or window overrides every default here. How an opening fits into the sequence of framing a wall is in the guide to framing a partition wall; steel openings are covered in the metal vs wood studs guide.
Two worked examples
A 36 × 80 in pre-hung interior door
- Width: 36 + 2 = 38 in; height: 80 + 2-1/2 = 38 × 82-1/2 in
- Header: 38 + 3 = 41 in
- Jacks cut to 82-1/2 in; kings full height; 2 cripples about 6-5/8 in long above the header
The short cripples above an 8 ft wall’s door are why many framers use a header made of two flat 2 × 4s with a 2 × 4 cripple layer, or fill the space with a solid 2 × 6 header instead.
A 35-1/2 × 59-1/2 in window with its sill 30 in above the floor
- Rough opening: 35-1/2 + 1/2 = 36 in by 59-1/2 + 1/2 = 36 × 60 in
- Header: 39 in
- Jacks: 28-1/2 in below the opening plus 60 in, cut to 88-1/2 in
- Cripples: 2 above (about 29-1/8 in), 2 below (about 27 in)
The window’s own rough opening on its label wins if it differs; window sizes are often called by their rough opening, so check which number you have.
Where to find your inputs
Door or window size. The slab size printed on the door’s edge or the box (a “2/8 × 6/8” door is 32 × 80 in); the window’s unit size or rough opening on its label or catalogue page.
Floor still to come. The thickness of tile and setting bed, or hardwood, that will be installed after framing.
Sill height. For windows, the height from the floor to the bottom of the rough opening.
Wall height. Floor to the underside of the top plates’ upper face; 97-1/8 in for a standard 8 ft wall.
Common mistakes
- Framing to the slab size. The door needs room for its jambs and shims; the opening is bigger than the door.
- Forgetting the floor. A door framed before a 3/4 in hardwood floor drags on it. Add the floor.
- Using a door rule for a window. Windows use their own rough opening; it is on the label.
- A pocket door in a wall with a pipe. The pocket must be clear the whole width; check before framing.
- Header sized by habit in a bearing wall. Use the span tables.
- Out-of-plumb jacks. A twisted opening hangs a door crooked forever. Check plumb and square before the board.
Questions people ask
- What is the rough opening for a 32 inch door?
- For a pre-hung interior door, 2 in wider and about 2-1/2 in taller than the slab: 34 × 82-1/2 in for a 32 × 80 in door. That leaves room for two 3/4 in jambs and about 1/4 in of shims on each side, and a gap under the door. Check the maker's sheet; some list 33-1/2 or 34-1/2 in.
- What is the rough opening for a 36 inch door?
- For a pre-hung interior door, 38 × 82-1/2 in. Exterior pre-hung doors are often slightly larger; many makers give the rough opening as the unit's outside frame size plus 1/2 in each way.
- How big is the rough opening for a window?
- Window makers generally give the rough opening as the unit dimensions plus 1/2 in in width and height, which leaves 1/4 in on each side for shims and insulation. Always use the rough opening printed in the window's catalogue or on its label.
- How wide is a pocket door rough opening?
- Twice the door width plus 1 in, and the door height plus about 4-1/2 in, for most pocket door frame kits: 61 in wide and 84-1/2 in tall for a 30 × 80 in door. The wall must have room for the door to slide into the pocket.
- How long is a door header?
- The rough opening width plus 3 in, so it bears on a 1-1/2 in jack stud at each end. A 38 in opening takes a 41 in header. In a non-bearing wall a flat or doubled 2 × 4 is usual; a bearing wall needs a header sized from the span tables.
- Should I add for the floor in a door rough opening?
- Yes, if tile, wood or another floor will be laid after framing. Add its thickness to the height so the door clears it; 3/4 in for hardwood is common. Carpet is usually allowed for in the standard 1/2 in gap under the door.