Builders call it a 2/6 — “two-six” — for 2 feet 6 inches wide, and it is one of the two most common passage doors in American housing. A 30 x 80 interior door measures 30 inches wide by 80 inches tall (6 feet 8 inches, the standard door height in homes built after the mid-20th century) and shows up on bedrooms, bathrooms, and offices in millions of houses. Because the size is a true commodity, it is cheap, stocked everywhere, and available in every style — but ordering one still trips people up on rough openings, handing, and slab-versus-prehung decisions. Here is everything that matters, with the actual numbers.
Where 30-Inch Doors Belong
The 30″ width is the workhorse for bedrooms and full bathrooms — wide enough to move a queen mattress or a dresser through with the door open, narrow enough to fit typical hallway wall segments. Codewise, the IRC requires only that habitable rooms have a door; there is no minimum passage-door width for existing bedrooms, though 32″ clear width is the accessibility benchmark (a 30″ door yields roughly 28″ of clear passage with the slab open 90 degrees, hinges and stops subtracted). That is the practical caveat: for aging-in-place plans or wheelchair access, upsize to a 32″ or 36″ door — or fit swing-clear offset hinges, which recover almost 2″ of clearance from an existing 30″ opening for about $40 a pair. Closets, half-baths, and pantries often step down to 28″ or 24″; main entries into rooms rarely go below 30″ in modern layouts.
Rough Opening Math
The framing formula for a prehung interior door is add 2″ to the width and 2 to 2 1/2″ to the height:
- Rough opening for a 30 x 80 prehung: 32″ wide x 82 to 82 1/2″ tall.
The width breaks down as 30″ slab + two 3/4″ jamb legs + about 1/2″ total shim space. Height allows for the head jamb, shim space, and clearance under the slab for flooring — figure the bottom of the slab finishing 1/2″ to 3/4″ above the finished floor (more if carpet is coming). Measure the rough opening at three points for width and both sides for height, and check the sill plate for level: an out-of-level floor means you will trim one jamb leg so the head stays level. Standard jamb width is 4 9/16″ for 2×4 walls with 1/2″ drywall both sides; 2×6 walls take 6 9/16″ jambs — order the wrong depth and your casing will not sit flat.
Slab vs Prehung
A slab is the bare door; a prehung arrives hinged in its frame with the jamb assembled. The decision rule is simple: replacing a damaged door in a good existing frame, buy a slab; anything else — new construction, remodels, racked or painted-shut frames, or any project where the old door does not close nicely today — buy prehung. Hanging a slab in an existing frame means mortising hinges to match existing locations to within 1/16″ and boring the lock hole to align with the existing strike, which is fussy router-and-chisel work. Setting a prehung is 45 minutes with shims, a 6-foot level, and 2 1/2″ screws through the hinge-side jamb into the trimmer. Price difference at big-box stores is modest: a 6-panel hollow-core molded slab runs $40 to $70, and the same door prehung runs $120 to $180 — the $80 premium buys a perfectly fitted frame.
Hinge, Bore, and Handing Specs
Stock 30 x 80 interior doors follow standardized hardware specs worth knowing before you order or drill:
- Hinges: three 3 1/2″ x 3 1/2″ radius-corner (5/8″) butt hinges on prehungs. Standard placement: 7″ from the top of the door to the top of the upper hinge, 11″ from the bottom to the bottom hinge, middle hinge centered. Hollow-core slabs under 1 3/8″ thickness can technically hang on two hinges, but three is the stock standard.
- Thickness: interior doors are 1 3/8″; exterior doors are 1 3/4″. Buy interior locksets accordingly.
- Bore: a 2 1/8″ diameter cross bore, centered 36″ to 38″ from the door bottom (backset lore: the bore center sits at a 2 3/8″ backset from the door edge — the residential standard; commercial hardware uses 2 3/4″). The edge bore for the latch is 1″. Virtually every Kwikset, Schlage, and Defiant residential knob or lever fits this prep.
- Handing: stand on the side where the door swings toward you; if the knob is on the left, it is left-handed. Prehungs must be ordered handed; slabs without bores are reversible.
What Is In Stock at the Big-Box Stores
Home Depot and Lowe’s keep 30 x 80 in more styles than any width except 32″. Expect on-the-shelf availability of: 6-panel molded hollow-core (the builder classic, $45–$70 slab), 2-panel and 3-panel Shaker molded doors ($60–$110 slab / $150–$230 prehung — the current remodel favorite), flush hardboard ($40–$60, the cheapest option), and 5-panel equal in many markets. Solid-core versions of the popular molded styles — worth the upgrade for bedrooms and baths, cutting through-door sound noticeably — run $110 to $180 as slabs and $220 to $320 prehung. True stile-and-rail solid wood (knotty pine, poplar, oak) climbs to $250 to $600. French/glass-lite and louvered doors in 30″ width are typically special order, arriving in 1 to 2 weeks. Nearly all stock doors come primed; factory-painted programs add $40 to $75 and save you two coats of enamel per side.
Trimming a 30-Inch Door to Fit an Older Opening
Pre-war houses rarely frame to modern sizes, so a stock 30″ slab often needs shrinking to fit a 29 1/2″ x 78 3/4″ opening. The rules that keep you out of trouble:
- Know your door’s guts. Solid wood and solid-core doors trim generously. Hollow-core molded doors have only about 1 1/8″ of solid lumber rail at the bottom and roughly 3/4″ to 1″ stiles at each edge — trim beyond that and you expose the cardboard honeycomb. Removing more than about 1″ total usually means re-gluing the cut-off rail piece back into the opened bottom as a filler block.
- Split width cuts between both edges (a saw pass off each stile) to keep the lock stile and hinge stile symmetrical — critical if the door is already bored.
- Cut with the show face taped and scored. Painter’s tape plus a utility-knife score line along the cut, then a circular saw with a 40-tooth blade against a clamped straightedge, prevents veneer chipout. A track saw makes this foolproof.
- Plane, don’t saw, small amounts. Under 1/8″, use a power planer or hand plane on the hinge edge, and re-bevel the lock edge 2 to 3 degrees toward the stop so it clears as it swings.
- Seal all cut edges with primer or paint — raw bottom edges wick bathroom humidity and swell, which is why so many old bathroom doors stick every summer.
Pocket, Barn, and Bifold Variants
The 30 x 80 slab size carries over to space-saving formats. A pocket-door conversion uses a standard 30″ slab in a frame kit (Johnson Hardware 1500 series, $120–$180 plus the slab) but requires opening the wall and a rough opening roughly double the door width — a remodel-scale job worth it in tight bathrooms. Barn-door hardware suits a 30″ opening best with a wider slab (36″ to 42″) to overlap the casing, so the door itself steps up a size; remember barn doors seal poorly for sound and are a weak choice for bathrooms. Bifold and bypass closet doors in 30″ width are stocked in the same styles and run $60 to $150. In every case the 80″ height stands — true 7-foot (84″) and 8-foot (96″) doors are a special-order upcharge of 50 to 100 percent and belong to newer custom homes.
Bottom Line on Budget
All-in numbers for one 30 x 80 interior door: hollow-core prehung plus a $25 Kwikset passage knob, shims, and casing lands around $180 to $260 DIY. Upgrading to solid-core pushes materials to $280 to $400. Professional installation adds $150 to $350 per door (less per door in multiples), and slab-in-existing-frame fitting bills similarly because of the mortising labor. For a whole-house refresh, replacing every dated 6-panel with prehung Shaker doors runs roughly $350 to $500 per opening installed — one of the highest-perceived-value interior upgrades per dollar, and with a 30 x 80 interior door being the commodity it is, availability will never be your problem.
