Door Casing Calculator

1. Enter the number of doors you need to case.
2. Enter the door height and width in inches. Standard interior doors are 80 inches tall and 32 inches wide.
3. Enter the casing width. The most common residential casing is 2-1/4 inches (colonial or ranch profile).
4. Enter the reveal, the setback from the edge of the jamb. Standard is 1/4 inch.
5. Choose a waste factor. Use 10 percent for simple installations, 15 percent if you have many miter cuts.
6. Choose the stock length available at your supplier. Pre-cut door casing is often 7 feet; general trim comes in 8 or 12 feet.
7. Optionally enter a price per linear foot to see a cost estimate.

Here is what each result line means:

For the rough opening behind the casing, see the rough opening calculator.

A door casing calculator estimates how many linear feet of trim you need to install casing (also called architrave or door trim) around a set of doors. It accounts for the casing width, the reveal setback and a waste factor for miter cuts and offcuts.

Trim carpenters, contractors and homeowners use it to order the right amount of casing stock and to estimate project cost before buying materials.

Each door has three casing pieces in a standard installation: two vertical side pieces (legs) and one horizontal top piece (head). The calculator adds the reveal to each piece so the casing extends past the jamb edge, then converts the per-door total from inches to feet.

1. Add the reveal to the door height to get the leg length.
2. Add twice the casing width and twice the reveal to the door width to get the head length. The casing width extension lets the head cover the top of each leg at a miter joint.
3. Sum two legs and one head, divide by 12 to convert to feet.
4. Multiply by the number of doors for the net linear footage.
5. Apply the waste factor and divide by stock length to get the number of pieces.

You are casing 5 interior doors, each 32 x 80 inches, with 2-1/4-inch colonial casing and a 1/4-inch reveal. You want 10 percent waste and will buy 7-foot stock.

Result: Each leg is 80.25 inches. The head is 37 inches. Per door that is 197.5 inches or 16.46 feet. Five doors need 82.29 net feet. With 10 percent waste the total is 90.52 feet. At 7-foot stock you need 13 pieces. At $1.75 per linear foot the cost is about $158.

Door Size

Taller or wider doors need more casing per opening. An 80-inch door uses about 13.4 feet of leg material, while a 96-inch (8-foot) door uses about 16 feet of leg material, before the head piece.

Casing Width

Wider casing profiles add material to the head piece. A 3-1/2-inch craftsman casing adds 2.5 more inches to the head than a 2-1/4-inch colonial casing (5 extra inches total for both sides). Over many doors this adds up.

Reveal Size

A larger reveal extends every piece slightly. Increasing from 3/16 inch to 1/4 inch adds 1/8 inch per joint (5 joints per door), which is small per door but measurable across a house with 20 or more doors.

Joint Style

Mitered corners (45-degree cuts where legs meet the head) require extra material for test cuts. Butt joints (head sits on top of square-cut legs) waste less but the head piece is narrower because it does not extend past the legs.

Number of Sides Cased

Closet doors or pocket doors may be cased on only one side. The calculator assumes both sides are cased from one face. Multiply by two if you are casing both faces of a pass-through opening.

Casing prices vary by profile, material and finish. Here are common ranges for 2-1/4-inch casing at US retail prices.

These prices cover the casing material only. Add labor ($2 to $5 per linear foot installed) and paint or stain for a complete estimate. The calculator uses your entered price for a project-specific total.

New Construction Trim-out

Run the calculator for every door in the house before ordering casing. Group doors by size to minimize different stock lengths.

Renovation or Remodel

When replacing old casing, measure the existing reveal and casing width to match the profile. The calculator tells you exactly how much stock to buy.

Comparing Casing Profiles

Enter different casing widths to see how a wider craftsman profile changes the material total compared to a standard colonial. Wider profiles use more linear feet per door.

Budget Estimation

Enter the price per foot to compare MDF, pine and oak options before committing to a material. The cost scales linearly with the number of doors.

1. Forgetting the Reveal

The reveal is the small setback from the jamb edge that gives the casing a shadow line. Omitting it shortens every piece by the reveal amount, and short legs leave a gap at the floor.

2. Not Adding the Casing Width to the Head

On a mitered installation the head must extend past the door opening by the casing width on each side. Using just the door width for the head leaves the miter joint short.

3. Measuring the Rough Opening Instead of the Door Opening

The rough opening is wider and taller than the finished door opening by the shim space. Casing sits on the jamb, which fits inside the rough opening, so use the jamb (door) dimensions.

4. Underestimating Waste for Miter Cuts

Every miter cut removes a triangle of material from the end of the board. With 7-foot stock and two miter cuts per piece, you can lose 2 to 4 inches per piece. Use at least 10 percent waste.

5. Mixing Up One-sided and Two-sided Casing

A pass-through opening or a cased opening with no door needs casing on both faces. The calculator covers one face per door. Double the result for two-sided openings.

The calculator estimates casing material for standard three-piece door trim (two legs and one head) with mitered or butt joints.

A standard 32 x 80 inch door with 2-1/4-inch casing and 1/4-inch reveal needs about 16.5 linear feet of casing (two 80.25-inch legs and one 37-inch head).

The reveal is the small setback (usually 3/16 to 1/4 inch) between the edge of the door jamb and the inside edge of the casing. It creates a shadow line and hides slight irregularities in the jamb edge.

The most common residential door casing is 2-1/4 inches wide (often called colonial or ranch style). Craftsman-style casing is typically 3-1/2 inches wide. Widths of 2-1/2 inches are also available.

An interior door in a wall is cased on both faces, but each side is a separate installation. The calculator covers one side. For a standard door in a wall, run the calculation for one side per door since both sides use the same amount of trim.

Allow 10 percent for straightforward installations with mitered corners. Use 15 percent if you are working with hardwood or making many test cuts. Use 20 percent for complex profiles or if you are less experienced with miter saws.

Pre-cut door casing kits come in 7-foot lengths (two legs and one head). For doors taller than 80 inches or for more flexible cutting, buy 8-foot or 12-foot boards and cut to length.

The same formula works for the two sides and head of a window. Windows also need an apron or stool piece at the bottom. Add the window width plus extensions for the apron length, which this calculator does not include.

Casing is the specific trim that frames a door or window opening. Trim is the general term for all decorative molding including casing, baseboard, crown molding and chair rail.

Plinth blocks are decorative blocks at the base of the casing where it meets the baseboard. They shorten the leg by the height of the plinth block. Subtract the plinth block height from the leg length if you are using them.

No. The calculation runs entirely in your browser and nothing you enter is stored or sent anywhere.

• InchCalculator, Trim and Molding Calculator (casing per door formula, stock length guidance, window and door casing dimensions).
• Power.one, Trim Casing Calculator (door casing linear feet formula: 2 legs plus 1 head with trim width allowance).
• Homewyse, Cost to Install Door Casing 2024 (door casing material and labor cost ranges by region).