Interior door calculator

Every line shows the quantity to buy and how StudSheet got it: the spacing, the waste and the package size, so you can check it before the supply house or the quote.

In Canada (762 mm × 2.03 m door)

Set to Canada, the Sheet works the job out again for Ontario: metric sizes, bag sizes, the frost depth and the code notes. It doesn't just convert feet to meters. The first lines:

• 1 door, Prehung interior door, hollow core: A prehung unit, hollow core, split jamb with the casing attached. Order the hand: left-hand means the hinges are on the left when the door opens toward you. Primed, ready to paint.
• 1 pack, Wood shims, 12-pack: Pairs behind each hinge and the latch, and at the head: about 12 shims a door.
• 1 box, Finish nails for a hammer, 0.5 kg box: About 30 a door through the jamb and shims, and 16 for the casing = 46 (about 140 a box). With a finish nailer, a box of 64 mm and 38 mm gun nails instead.
• 1 pack, Hinge screws, 76 mm: One 76 mm screw replaces a short one in each hinge, into the stud: 3 for 1 door with 3 hinges.
• 1 set, Door knob or lever set: A passage set latches but doesn’t lock: halls, closets, most rooms.
• 1 stop, Door stop: Keeps the knob out of the wall behind the door.

1. Take out the old door: pry off the casing on both sides, cut the nails behind the jamb with an oscillating tool, and pull the old frame.
2. Check the opening: plumb the hinge-side stud with the long level, check the floor for level and the diagonals for square.
3. Set the prehung in, hinge side first: shim behind each hinge until the jamb is plumb and straight, then nail through the jamb and the shims (the split jamb’s first half goes in from the swing side).
4. Shim and nail the latch side for an even ⅛″ gap at the door, then shim the head.
5. Replace one screw in each hinge with a 3″ screw into the stud.
6. Check the swing (the door stays wherever you leave it), the gap at the head and the latch; snap the shims off flush.
7. Casing: slide the second half of the split jamb in from the other side, tight to the wall, and nail it.
8. Install the passage set and the stop; adjust the strike so the latch catches without rattling.
9. Paint: fill the nail holes, caulk the casing to the wall, then two coats of semi-gloss on both faces and all six edges.

Must-have tools first, then the ones that help and the ones to rent for the day.

Mistakes that cost a callback or a second trip

• Ordering the wrong hand: A left-hand door can’t become a right-hand one. Stand where the door opens toward you: the hinges are on its hand.
• Hinge jamb not plumb: The door swings open or closed by itself. Plumb the hinge side over its full height before you nail.
• Over-shimming: Shims driven too hard bow the jamb, and the door rubs. Snug, then check the gap.
• Nailing where there’s no shim: The jamb pulls in at the nail. Nail through the shims.
• No long hinge screw: The door sags and drags at the latch within months. One 3″ screw per hinge into the stud.
• Painting only the faces: An unsealed top and bottom edge take on moisture and the door warps. Seal all six edges.

What the calculator assumes

• Rough opening about the door’s width + 2″ by its height + 2½″ (prehung makers’ install sheets); ⅛″ gap at the latch and head.
• Casing (flat jambs): legs from the floor to the top of the head, heads the door’s width + 2 × (reveal + 2¼″ casing), mitered; cut from the cheapest store lengths.
• Shims: a 12-pack a door; nails about 30 a door plus the casing; one 3″ screw per hinge (3 hinges on an 80″ door, 4 on a 96″ one).
• Paint: both faces +15% for edges and panels, plus about 8 sq ft of jamb and casing a door, 2 coats at 350 sq ft per gallon.

The Sheet sets its code notes for the job's state or province. These are New Jersey's and Ontario's; the code reference has more. Always confirm with your building department.

• Carpet under the door: Over carpet the door needs ¾–1″ of clearance under it; most prehung units leave about ½″. Set the jamb on scraps of the carpet’s thickness, or trim the door bottom with a circular saw and a straightedge (score the line first). Hollow-core doors take about ¾″ off before the bottom rail runs out.

What materials do I need to hang an interior door?

For the worked example, a 30″ × 6′ 8″ door, the Sheet counts 9 lines with waste included, starting with prehung interior door, hollow core (1 door), wood shims, 12-pack (1 pack), finish nails for a hammer, 1 lb box (1 box), hinge screws, 3″ (1 pack). Each line's math is in the table above. Put in your own sizes in the interior door calculator and every line is counted again.

How long does it take to hang an interior door, and can I do it myself?

About 4 to 6 hours for the worked example, in 9 steps. StudSheet stamps it DIY OK: you can do this.

What tools do I need to hang an interior door?

18 in all. The must-haves start with 6-ft level, 4-ft level, tape measure (25 ft), carpenter's pencil, utility knife + blades, framing hammer. On the Sheet you mark each one as owned, to buy or to rent.

Stuck while you hang an interior door? Ask in the Interior doors group of the StudSheet community with this Sheet attached. Homeowners who've done it and verified pros answer, and anyone can read it.

• Carpentry and framing for contractors: run this takeoff at your own prices, send the estimate, and get it signed and the deposit paid.
• All 45 Sheets, across 16 trades.
• Code reference: frost depths, guard heights, stairs, retaining walls.