How to calculate crown molding
Crown follows the whole perimeter of the room — and unlike baseboard, it never stops for a doorway:
Linear feet = perimeter × (1 + waste %)
Perimeter is 2 × (length + width). Add your waste allowance for mitered and coped corners, then divide by your piece length and round up to whole pieces. Because crown passes above doors and windows, there are no openings to subtract.
Common molding lengths
| Piece length | Good for |
|---|---|
| 8 ft | Easy to handle; most rooms |
| 12 ft | Fewer seams on long walls |
| 16 ft | Long, unbroken runs |
Tips for cleaner corners
- Cope inside corners. Coping one piece over a square-cut mate hides gaps better than a compound miter — and handles out-of-square walls.
- Use a crown jig or chart. Compound miters are easy to cut backwards; mark your spring angle and test on scrap first.
- Scarf the long runs. Join pieces mid-wall with a 45° scarf joint so the seam nearly disappears.
- Prime and paint first. Finishing before installing means only the nail holes and seams need touch-up.