Crown Molding Calculator: Pieces & Linear Feet

1. Measure your room — enter the length and width in feet. Most rooms only need these two numbers.
2. The calculator adds them and doubles the total to get the ceiling perimeter, which is the run your crown molding follows.
3. It adds a waste allowance (10% by default) to cover the angled cuts at every corner.
4. It divides by your stock length (8 ft by default) and rounds up to whole pieces — you can only buy full sticks.

Open More options to switch to metric, choose 10 / 12 / 16 ft stock, change the waste %, add a spare piece for repairs, or enter a price per foot for a quick cost estimate.

Crown molding is sold by the linear foot and installed in whole sticks, so the two numbers that matter are the total run around the room and the length of each piece. The run is simply the ceiling perimeter: 2 × (length + width) for a rectangular room.

One thing that surprises first-timers: unlike baseboard, you do not subtract doors and windows. Crown molding runs along the top of the wall where it meets the ceiling, so it passes uninterrupted above every opening — the full perimeter is in play.

Waste matters more for crown than for flat trim. Each inside and outside corner needs a mitered or coped cut, and every cut shortens the usable stick. A 10% allowance is a safe default for a simple rectangular room; add more if the room has many corners, bump-outs, or you are new to coping joints.

Perimeter = 2 × (length + width)

Linear feet needed = perimeter × (1 + waste% ÷ 100)

Pieces to buy = round up ( linear feet needed ÷ stock piece length )

Total purchased = pieces × stock length

Example: a 12 ft × 10 ft room has a perimeter of 2 × (12 + 10) = 44 ft. With 10% waste that is 48.4 ft. Divided by 8 ft sticks: 48.4 ÷ 8 = 6.05, which rounds up to 7 pieces (56 ft purchased, about 7.6 ft left over).

A 10 × 12 bedroom: perimeter = 2 × (10 + 12) = 44 ft. Add 10% waste → 48.4 ft. At 8 ft per stick that is 7 pieces.

A larger 15 × 20 living room: perimeter = 2 × (15 + 20) = 70 ft. Add 10% → 77 ft. Switching to 16 ft stock in More options: 77 ÷ 16 = 4.8 → 5 pieces, with far fewer seams to hide.

Adding cost: for the 10 × 12 room at $8 per linear foot, 56 ft purchased × $8 ≈ $448 in material before paint and hardware.

- Buy longer sticks for long walls. A single 16 ft piece beats two 8 ft pieces with a seam in the middle.
- Keep the spare-piece option on for your first crown project — coped corners are unforgiving, and a botched cut is cheaper to replace than a second store trip.
- Round up per wall, not just overall, if your walls are longer than one stick — you cannot splice offcuts across a coped corner.
- Paint or prime before installing. Touch-ups in the corner joints are easier when the profile is already sealed.
- Confirm the profile is in stock in the length you plan on; not every store carries 16 ft crown.