Window / Door Rough Opening Size
The rough opening to frame from a unit size.
Example
You enter
- Opening type prehung-door
- Unit width (in) 36
- Unit height (in) 80
- Width adder override (in, -1 = convention) -1
- Height adder override (in, -1 = convention) -1
You get
- Ro width (in) 38
- Ro height (in) 82.5
- Header rough length (RO + two jacks) 41.00 in
- Wa used 2
- Ha used 2.5
Checked against published worked examples from: US framing convention.
Details, formula, and sources
Scopeby the published conventions - a window frame + 1/2 in each way (1/4-in shim per side), a prehung door SLAB + 2 in wide and 2.5 in tall (a 36 x 80 door wants a 38 x 82.5 RO - measured from the slab, not the jambs). Adds the header rough length (+ two 1.5-in jacks) and exposes the adders as overrides, because the manufacturer's stated RO governs whenever it differs.
Formula or tableWindow: RO = frame outside dimension + 1/2 in each way (1/4-in shim per side). Prehung door: RO = SLAB + 2 in wide, + 2.5 in tall. Header rough length = RO width + 3 in (two 1.5-in jack studs). Adders editable.
Source and editionThe widely published US framing conventions for rough openings, stated as DEFAULTS - not a code section; the unit manufacturer's stated RO governs whenever it differs.
Free accessThe conventions are published freely across framing references and every window/door manufacturer's installation instructions.
What governsEstimate. AHJ and licensed professional govern.
API field namesopening_type, unit_width_in, unit_height_in, width_adder_in, height_adder_in, ro_width_in, ro_height_in, header_length_in, wa_used, ha_used
- Window adder 1/2 in over the frame outside dimension in each directionpublished framing convention; manufacturer RO governs
- Prehung-door adder 2 in wide / 2.5 in tall over the slabpublished framing convention; manufacturer RO governs
- Header length RO width + two 1.5-in jack studsstandard platform-framing practice