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The receipt said 30. The opening wanted 29¾. A quarter inch cost a carpenter most of an afternoon.

I measure twice now. Not careful by nature. I’ve just seen what happens when someone isn’t.

Interior swinging door installation isn’t skilled work so much as careful work.

How to Measure & Install Interior Swinging Doors

Why Swinging Doors Still Dominate Interior Openings

Pocket doors photograph well. Tracks develop slopes nobody notices until the door drifts open at 2 a.m. and you’re standing in the hallway wondering whether you closed it or not.

Barn doors. Rattling. Air leaking around the edges. Hardware often costs more than a decent prehung unit, and you still hear every conversation through the gap.

Latch against a stop, continuous seal. Sound stays where you put it. Light doesn’t bleed under the slab. The door stays closed without being reminded. Weight across two or three hinges, so the slab holds its shape and the reveal stays even year after year. Builders keep specifying hinged assemblies for bedrooms, bathrooms, offices and hallways. Not habit. Function.

How to Measure & Install Interior Swinging Doors

Interior Door Measurements: Get These Right First

Slab, frame, rough opening. Three levels.

Width on the slab, from the middle. Hinge edge to latch edge, not frame to frame. Top and bottom checked, smallest reading. Height along the hinge side. Standard thickness 1⅜ inches, though older doors have their own ideas, so verify.

Nominal versus actual. A “32-inch door” measures about 31¾ wide. That quarter inch is hinge and latch clearance. Order to the nominal number and the door either won’t close or will close once and then swell shut in the first humid week. I’ve seen both. The second one is worse, because you don’t find out until the customer calls back.

Rough opening. Stud to stud, floor to header. Prehung wants roughly 2 inches more width than the door, about 82½ inches of height for an 80-inch door. Most openings are out of square. New construction included. Especially new construction, in my experience. Smallest dimension is the one that counts. The door fits the tightest point, not the average.

How to Measure & Install Interior Swinging Doors

Interior Swinging Door Installation: Hinges and Hardware

Placement and seating decide everything. Wrong and the door drags the stop, or sags, or both.

Top hinge about 7 inches down, bottom roughly 11 inches up. Residential defaults, fine for most hollow-core and molded doors. Solid-core or oversized doors need a third at mid-height. Omit it and the top corner sags within a year. A torn-out hinge never repairs as cleanly as the original mortise.

Trace the leaf on both the door edge and the jamb. Score with a knife before chiseling. Mortise to leaf thickness exactly, or the hinge sits proud and the door never closes flush.

Self-centering bit. Ten dollars. Before you drill three pilot holes off-center.

Wedges under the door, leaves aligned, screws through the jamb side. Gaps at top, hinge side, latch side, checked as you work. Even margins mean square.

Sagging? One short jamb screw swapped for a longer one that bites the wall stud. Minor binding? Thin shim behind a hinge leaf shifts the pivot point. Try that before reaching for a plane. Shims come out. Wood doesn’t go back.

How to Measure & Install Interior Swinging Doors

Where Swinging Doors Make Sense

Bedroom door replacements, bathroom entries, hallway transitions. Privacy and a clean sightline. The swing arc eats floor space, so compact closets and laundry rooms deserve a second thought. Standard room-to-room opening, though, the arc usually clears furniture. Home offices and guest rooms fit well too. Swinging door seals tighter than a pocket or barn door, costs almost nothing extra.

Standard butt hinges, hollow-core and molded doors. Spring hinges for garage entries and busy passages where a door left open becomes somebody else’s problem. Solid-core or heavy slabs, ball-bearing hinges are the one upgrade I’d insist on. Plain hinges wear faster under that load. The wear shows up as a sag you can’t shim out.

Hardware Sourcing

Hinge finish and screw colour matched before ordering, not after. Hinge size and leaf thickness against both the slab and the jamb. Mismatched leaves are one of the most common reasons a door won’t close properly. An hour spent diagnosing what a spec sheet would have told you in a minute.

Kanod prehung interior door systems and coordinated hinge sets ship as a matched unit. Slab, frame and hardware already compatible, which takes most of that mismatch risk off the table. Hallway involved? Kanod recommends ordering hardware in one batch so finishes and tolerances stay consistent door to door. Three slightly different hinge finishes along one hallway is the kind of thing you notice every day.