Crown Molding Calculator

The formula

Coverage and yield assumptions

Lumber yards stock most profiles in 8, 12 and 16 ft lengths; some MDF and polystyrene profiles come in 8 ft only. The 1 ft per corner allowance covers a practice cut and the length lost to the angle on wide profiles. Wide crowns (over 5 in) lose more at each miter.

Measuring for crown

Measure along the ceiling line of every wall, not the floor; built-ins, bulkheads and chimney breasts change the run. Each projection adds two outside corners. Write each wall on a sketch so you can plan which stick goes where and keep joints away from the room's focal point.

Coping vs mitering

Inside corners hold up better when coped: one piece runs square into the corner and the next is cut to the profile of the first. Outside corners are mitered. On long walls, join sticks with a scarf joint (two opposing 45° bevels) over a ceiling joist or blocking so the seam stays tight.

Spring angle and nailing

Most crown has a 38° or 45° spring angle, which sets how it sits against the wall and ceiling. Cut it upside down and backwards on a miter saw, or set a compound saw to the published angles for your spring. Nail into studs and top plates or add a continuous triangular backer strip so every piece is supported.

Choosing material

• Pine and poplar paint well and take a crisp profile.
• MDF is cheaper and stable but dents easily and swells in damp rooms.
• Polyurethane foam crown is light and moisture resistant, good for bathrooms.

Common mistakes to avoid

• Measuring along the floor instead of the ceiling line.
• Cutting crown flat on the saw without accounting for the spring angle.
• Ignoring bump-outs and chimney breasts, each of which adds two outside corners.
• Joining sticks with square butt joints instead of scarf joints.
• Nailing only to the wall when there is no backing at the ceiling.

Waste factor

Crown wastes more than flat trim because every corner loses a wedge and mistakes are common while learning the cuts. 15% is the default; experienced installers working with long sticks may use 10%, and rooms with many corners or a first-time installer should use 20%.

Imperial and metric

Switch the toggle above the inputs to enter ft ↔ m. The page converts metric entries to imperial before calculating, using NIST factors (1 ft = 0.3048 m, 1 in = 2.54 cm), and shows key results in both systems.

Worked examples

Bedroom, 4 corners

Inputs: room perimeter 52 ft; corners 4; piece length: 12 ft; waste factor 15%.

Result: Buy 6 pieces of crown molding.

• Units to buy (rounded up): 6 pieces
• Total with waste and corner allowance: 64 linear ft (19.4 m)

Living room with bump-out

Inputs: room perimeter 74 ft; corners 6; piece length: 16 ft; waste factor 15%; cost per unit $38.

Result: Buy 6 pieces of crown molding.

• Units to buy (rounded up): 6 pieces
• Total with waste and corner allowance: 91 linear ft (27.8 m)
• Estimated material cost: $228.00

Small bath, 8 ft MDF

Inputs: room perimeter 26 ft; corners 4; piece length: 8 ft; waste factor 20%.

Result: Buy 5 pieces of crown molding.

• Units to buy (rounded up): 5 pieces
• Total with waste and corner allowance: 35 linear ft (10.7 m)

Quick reference for common sizes

The table repeats the first worked example at smaller and larger sizes, keeping every other setting the same, so you can see how the crown molding calculator result scales.

Limitations

The calculator assumes straight walls. Curved walls, vaulted ceilings and stair runs need special techniques and extra stock. Count each column, hood or bump-out by measuring it separately.