Carpentry Calculators

Door and window casing calculator

Enter the openings, the casing width and the reveal. This gives every head, leg and apron to its long point, and packs them into the sticks you actually carry home.

Doors

Cased on
in

Inside the jamb

in

Floor to the head jamb

Windows

Trimmed as
in

Inside the jamb

in

Stool top to the head jamb

Casing

in

= 2.25"

in

= 0.188"

ft

Usually 7, 8, 14 or 16

in

= 0.125"

in

= 0.75"

Sticks of casing

19× 7 ft

Casing, laid end to end

112.9 ft

Miter

45.0°

Pieces

24

  • Every piece comes out of one stick — passesThe longest piece is 82 7/16", inside a 7 ft stick.

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36 7/8"82 7/16"40 7/8"50 7/16"

Cut list

Door head (32" × 80")45° both ends, long point to long point
4 × 36 7/8"
Door leg (32" × 80")45° at the top, square at the foot
8 × 82 7/16"
Window head (36" × 48")45° both ends, long point to long point
3 × 40 7/8"
Window leg (36" × 48")45° at the top, square at the foot
6 × 50 7/16"
Apron (36" × 48")Square both ends
3 × 40 7/8"

Stool stock, bought separately

Stool (36" × 48")Before notching the horns around the jamb
3 × 42 3/8"

Out of 7 ft sticks

8 sticks1 9/16" left over on each
82 7/16"
6 sticks33 9/16" left over on each
50 7/16"
3 sticks2 1/8" left over on each
40 7/8" + 40 7/8"
2 sticks10 1/8" left over on each
36 7/8" + 36 7/8"

The same cuts from other lengths: 16 × 8 ft, 9 × 14 ft, 8 × 16 ft. Kerf is charged between pieces; miters are not nested, so this never asks for too little.

Measure the opening, not the door

Width is inside the jamb, edge to edge; height is from the finished floor to the underside of the head jamb. If the finished floor is not down yet, a leg measured from the subfloor is long by the floor's thickness — cut the legs once it is in, or cut them long and trim.

The lengths here are long points on a flat wall. Jambs that stand proud of the drywall or a wall that is out of plumb open a miter no matter how true the cut, so cut the head first, hold it up, and mark the legs from it.

Where to buy this

Buy every stick in one trip: profiles drift between runs, and two that nearly match never do at a miter.

Plain search links, nothing sponsored. Prices and stock are the shop's, and a local lumberyard will usually beat both on solid stock.

About door and window casing

How long is the head casing on a 32 inch door?
With 2 1/4" casing on a 3/16" reveal, the head is 36 7/8" long point to long point: the 32" opening, a reveal each side, and a casing width each side. Each leg is 82 7/16" — the 80" opening plus one reveal and one casing width, because a leg stands on the floor and only gets them at the top. Every cut is 45°.
How much casing do I need for one door?
Two legs and a head a face — 16.8 ft of casing for a 32" x 80" door in 2 1/4" trim. But it is bought by the stick, not by the foot: each leg nearly fills a 7' stick on its own, so one face takes 3 sticks of 7' and an interior door cased on both faces takes 5. Cased on both faces out of 14' stock it is 3 sticks, because two legs share one.
Why is door casing sold in 7 foot lengths?
Because a standard 6'8" door's leg just fits one. At 2 1/4" casing on a 3/16" reveal the leg is 82 7/16", leaving 1 9/16" of an 84" stick for squaring a damaged end. A wider casing or a taller door can push the leg past 84", and the calculator says so rather than splicing a leg — go to 14' stock for those.
What is the reveal on door casing?
The strip of jamb edge left showing inside the casing — the casing is set back from the jamb's inside face rather than flush with it. It is a choice, not a rule, and 1/8" to 1/4" is the usual range: a reveal hides a jamb edge that is not quite straight, where a flush joint shows every wander. Whatever you pick, it goes on both sides and the top, so the head grows by two reveals and each leg by one.
Should windows be picture-framed or trimmed with a stool and apron?
Either is right; it is a style. Picture framing miters casing all the way around, four pieces the same way a picture frame is made. A stool and apron puts a shelf-like stool at the bottom that the legs stand on, with an apron under it: for a 36" x 48" window in 2 1/4" casing, the apron is 40 7/8", the outside width of the casing, and the stool is 42 3/8" with a 3/4" horn past the casing at each end. The stool is a different profile of stock and is bought separately.

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