Interior Doors Calculator
How big should my door rough openings be? This free interior doors calculator gives DIYers and contractors a per-door schedule for the whole house — rough opening width and height, hinge count and size, lockset function and grade, specialty hardware (pocket frame, barn track, bifold kit, bypass kit, flush bolts, astragals, Dutch bolts), and the casing linear feet that feed the trim calculator — across 8 door types in one screen.
Pocket and barn doors are where rough-opening math goes sideways. Pocket frames vary by brand (Johnson 1500 = 2 × door + 1 in.; Eclisse Classic = 2 × door + 2 in.; Cavity Sliders TSC = 2 × door + 1-1/4 in.) — the calculator emits the conservative Johnson value with a brand-verification note. Barn doors size to opening + 4–6 in. with a track ≥ 2× slab width, rounded up to stock lengths (72, 78, 84, 96, 120, 144 in.).
Built on ICC IRC 2021 (R311.2 egress, R302.5.1 garage-to-dwelling, R308.4 safety glazing, R310 EERO), 2010 ADA Standards (404 clear width, 309 operable parts), ANSI/BHMA A156.1 / A156.2 / A156.13 / A156.18 (hinges, locksets, finishes, prep), NFPA 80 (fire-rated assemblies), and manufacturer technical data from Masonite, JELD-WEN, Reeb, L.E. Johnson, Eclisse, Real Sliding Hardware, Schlage, Hager, and Stanley.
Interior Doors Calculator
Per-door rough opening, hinge count and size, lockset, specialty hardware, casing LF, and code flags — across pre-hung, slab, bifold, bypass, barn, pocket, French / double, and Dutch.
Whole-house defaults
Door inventory
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How to Use This Calculator
- Pick whole-house defaults: jamb depth (4-9/16 in. for 2×4 walls / 6-9/16 in. for 2×6), casing profile (2-1/4 in. colonial WM 356 default), and finish grade (paint or stain — drives casing waste factor 10% vs 15%).
- Click "Load 3 BR / 2 BA preset" for a typical 14-door inventory, or "Add door" to build your own list one room at a time.
- For each door, set: room / location, type (pre-hung passage / slab / bifold / bypass / barn / pocket / French double / Dutch), construction (hollow core / solid core / solid wood / MDF / glass / steel-fire), width, height, and thickness.
- For bifold, bypass, and barn — also enter the opening width (track and panel sizing depend on it; pre-hungs and pockets size from the slab itself).
- Pick lockset function (passage F75 / privacy F76 / keyed F81-F82 / dummy / pocket privacy or pocket passage with edge pull) and hardware finish (619 satin nickel default).
- Toggle code flags per door: adjoins garage (R302.5.1), opens into a sleeping room (prohibited from the garage), has glass (R308.4 safety glazing), and self-closer required.
- Click Calculate — see per-door rough openings, hinge count and size, casing LF, plus an aggregated hardware bill (kits, hinges by size, locksets by function, pulls, bolts, astragals, stops) and explicit code-flag warnings for IRC R311.2 / R302.5.1 / R308.4 violations.
How the egress and garage-door checks work
IRC R311.2 requires at least one egress door per dwelling that provides ≥ 32 in. clear × ≥ 78 in. clear opening, side-hinged. The clear width is measured between the face of the door and the stop with the door open 90° — door thickness, hinge offset, and stop reduce a nominal width by approximately 2–2-1/2 in., so a 36 in. nominal door is required to net the 32 in. clear. The calculator flags any house where no specified swing door is 36 in. × 80 in. or larger. IRC R302.5.1 requires the garage-to-dwelling door to be solid wood or solid / honeycomb-core steel ≥ 1-3/8 in., or a 20-minute fire-rated assembly with self-closer. A door from the garage may NOT open into a sleeping room — the calculator emits an explicit error if you toggle "adjoins garage" + "opens into a sleeping room" on the same door. IRC R308.4 requires safety glazing (tempered or laminated) on all glass within doors and within a 24-inch arc of door edges below 60 in. AFF — toggle the "has glass" checkbox and confirm safety glazing per spec sheet.
Frequently Asked Questions
What rough opening do I need for a pre-hung interior door?
For a single pre-hung swing door: rough opening width = door width + 2 inches; rough opening height = door height + 2-1/2 inches. The 2-inch width allowance covers ~3/4 inch of jamb stock on each side plus ~1/4 inch of total shim and adjustment space; the 2-1/2 inch height covers the head jamb plus a floor-to-jamb gap for finished flooring. Examples: a 30 × 80 inch pre-hung needs RO 32 × 82-1/2 in.; a 36 × 80 inch needs 38 × 82-1/2 in. This is the universal rule across EZ-Hang, Builders Surplus, MMI Door, Masonite, and JELD-WEN install guides.
What rough opening does a pocket door need?
The conservative Johnson 1500-series formula is: RO width = (2 × door width) + 1 inch; RO height = door height + 4-1/2 inches. So a 30 × 80 inch pocket door needs 61 × 84-1/2 in.; a 36 × 80 needs 73 × 84-1/2; a 36 × 96 needs 73 × 100-1/2. Pocket frames vary by brand: Eclisse Classic uses 2W + 2 in.; Cavity Sliders TSC uses 2W + 1-1/4 in. Verify against the specified frame brand before framing — the cavity is full wall thickness, so plumbing, electrical, and structural elements cannot be located in the pocket.
How wide should a barn door be for the opening?
Barn door width = opening width + 4 to 6 inches (2–3 inches of overlap on each side; 3 inches per side is the privacy default for bedrooms and bathrooms). Door height = opening height + 1 inch. Track length must be at least 2× the slab width so the door fully clears the opening — round up to the next stock length (72, 78, 84, 96, 120, or 144 in.). The track must lag into studs or a continuous 1×4 / 1×6 backer board screwed to studs along the entire length. Per Real Sliding Hardware, Rustica, and Goldberg Brothers technical sheets.
How many hinges does an interior door need?
Per ANSI/BHMA A156.1: 2 hinges for doors up to 60 inches tall (rare in residential), 3 hinges for 60–90 inch doors (standard 80 and 84 inch residential), 4 hinges for 90–120 inch doors (96 inch tall), and one extra hinge per additional 30 inches. Add one more hinge for any door heavier than 200 lb or wider than 48 inches regardless of height. A standard 30 × 80 inch interior door uses three 3-1/2 × 3-1/2 inch hinges. A 1-3/4 inch solid-core or fire-rated door bumps to 4 × 4 inch ball-bearing hinges; a 96 inch tall door takes 4 hinges; a 36 × 96 inch oversized door takes 4 hinges and may bump to 4-1/2 inch.
What does IRC R311.2 require for the egress door?
At least one egress door per dwelling must provide a 32-inch minimum clear width × 78-inch minimum clear height, side-hinged, openable from inside without a key or special knowledge. Clear width is measured between the face of the door and the stop with the door open 90° — door thickness, hinge offset, and stop reduce the dimension by approximately 2 to 2-1/2 inches, so a 36-inch nominal door is required to net the 32-inch clear opening. Other interior doors are not bound by R311.2 minimums (the code explicitly states 'other doors shall not be required to comply with these minimum dimensions'). The calculator flags any house where no specified door achieves the 36 × 80 minimum.
What does the door from the garage to the house need to be?
Per IRC R302.5.1: solid wood at least 1-3/8 inches thick, OR solid / honeycomb-core steel at least 1-3/8 inches, OR a 20-minute fire-rated assembly bearing a UL or Warnock Hersey label. The door must have a self-closing and self-latching device. Hollow-core is prohibited. The door from the garage may NOT open into a sleeping room — re-route through a habitable space (mudroom, hall, or stair landing). The standard residential spec is a 32 × 80 × 1-3/4 inch steel-clad 20-minute fire-rated pre-hung with three 4-inch ball-bearing hinges, keyed entry lockset, and self-closer.
Can I use a hollow-core door for a bedroom or bathroom?
It will pass code, but acoustic performance is poor. Hollow-core doors deliver STC 17–22 — about as much sound isolation as no door at all. Solid-core doors (particleboard or MDF core) deliver STC 28–35 and are the residential comfort upgrade. Solid wood stile-and-rail goes 30–35 STC depending on density; mineral-core acoustic doors with full-perimeter gasketing and a drop seal can hit 32–36 STC but are uncommon in residential interiors. The calculator defaults to solid core for bedrooms and bathrooms and hollow core for closets, pantries, and secondary spaces.
How is bifold sized — and how many panels do I need?
Bifold doors are sold per the nominal opening size, with the slab undersized 1/2 inch so the as-supplied panels fit the rough opening. Openings up to 36 inches use a single pair (2 panels). Openings 37–72 inches use a double pair (4 panels). Openings over 72 inches use a triple pair or custom configuration. RO width equals the nominal opening — no allowance added — and RO height is door height + 2 inches (a head jamb is mounted but no jamb sits on the slab). Examples: 36-inch closet → 2 panels at 18 inches each, 1 knob; 72-inch linen closet → 4 panels at 18 inches each, 2 knobs.
What hardware comes with a French / double door pair?
Six hinges (3 per leaf on standard 80-inch doors), 1 active lockset on the operating leaf, 1 dummy trim on the inactive leaf, 1 pair of flush bolts mortised into the inactive leaf at top and bottom, 1 astragal (vertical strip on the inactive leaf's meeting edge that overlaps the active leaf), and 3 strike plates (active lockset + top and bottom flush bolt strikes). Rough opening = (2 × door width) + 2 inches × door height + 2-1/2 inches. The active leaf carries the daily lockset; the inactive is bolted closed and only opened to move furniture. Glass in any door must be safety-glazed (tempered or laminated) per IRC R308.4.