A rough opening (RO) is the framed hole a door or window is installed into. It is slightly larger than the unit so you can shim it plumb, level and square. Framing an opening means replacing the studs you cut out with a structure that carries the load around the hole: a header across the top, jack studs that hold the header up, king studs that tie everything to the plates, and cripples that fill in above and below.
1. Get the rough opening size
Always start with the manufacturer's rough opening size — it is printed in the window or door catalogue and on the installation instructions. If you don't have it yet, these rules of thumb are close:
- Pre-hung interior or exterior door: door width + 2″, and 82 1/2″ high for a standard 6′ 8″ (80″) door. A 36″ door needs a 38″ × 82 1/2″ RO. The extra height allows for the head jamb and finished flooring.
- Window: usually 1/2″ to 3/4″ wider and taller than the window frame. A window with a 35 1/2″ × 47 1/2″ frame typically wants a 36″ × 48″ RO.
Decide the head height as well. Exterior doors and windows usually line up at the same height — commonly the top of the door RO — so the trim lines up around the room. For a window, the sill height is the head height minus the RO height.
2. Mark the opening on the plates
With the top and bottom plates tacked together, mark the edges of the rough opening, then mark a jack stud and a king stud outside each edge. Lay out your common studs as normal: any 16″ mark that falls inside the opening becomes a cripple; a mark that lands on a king or jack is simply skipped. Don't shift the layout to suit the opening — the sheathing and drywall still need studs on 16″ centres.
3. Cut the pieces
For an 8 ft wall (97 1/8″ to the top of a double top plate, 92 5/8″ precut studs) and a 38″ × 82 1/2″ door with a 2×10 header, the cuts are:
- King studs: full length, 92 5/8″ — one each side.
- Jack studs: RO height minus the bottom plate: 82 1/2″ − 1 1/2″ = 81″. One each side (two each side for wide openings; the code's header table says how many).
- Header: RO width plus one jack on each side: 38″ + 3″ = 41″. In a 2×4 wall, two 2×10s with a 1/2″ plywood spacer make 3 1/2″, flush with the studs.
- Cripples above: from the top of the header (82 1/2″ + 9 1/4″ = 91 3/4″) to the underside of the top plates (94 1/8″): 2 3/8″. Short cripples like these are often replaced by making the header deeper — a 2×12 header nearly fills the space.
For a window, add a rough sill (a flat 2× the width of the RO, sometimes doubled for wide windows) and bottom cripples on layout from the bottom plate up to the sill. With a 36″ sill height the bottom cripples are 36″ − 1 1/2″ sill − 1 1/2″ plate = 33″ long.
4. Assemble flat on the deck
Build the opening as a unit before standing the wall. Nail the king to the plates, nail the jack to the king (staggered 10d or 16d nails, or as your code's fastener schedule requires), set the header on the jacks and nail through the king into the header ends. Add the cripples on layout, toe-nailed to the header and nailed through the top plate. For a door, leave the bottom plate continuous while you build and stand the wall; cut it out of the opening afterwards, flush with the jacks. That keeps the wall straight while you lift it.
5. Check before you stand it
Measure the opening at the top, middle and bottom: widths should match within 1/8″. Measure the diagonals of a window opening — they should be equal. Check that the header is level and the jacks are tight under it. It is much easier to fix a 1/4″ error on the deck than after the sheathing is on.
Load-bearing or not?
Everything above applies to load-bearing walls — exterior walls and interior walls that carry joists, rafters or another floor. In non-bearing partitions there is nothing for a header to carry, and the IRC allows a single flat 2× over openings within limits (section R602.7.3). The calculator offers a "Flat 2×" header for that case. If you are unsure whether a wall carries load, treat it as bearing and ask your building department.
The wall framing calculator places the kings, jacks, header, sill and cripples for every opening you add, draws the elevation and lists the cut lengths. For header choices, read header basics.
Planning information only — framing and deck requirements vary by jurisdiction. Verify with your local building code or a licensed professional.