Crown Molding Calculator
Crown molding runs continuously around the top of a room where the walls meet the ceiling, passing above doors and windows, so the full ceiling perimeter needs covering. Because corners require compound miter or coped cuts that are easy to spoil, a generous waste allowance is wise. Enter the ceiling perimeter in feet, a waste percentage, and the stick length you plan to buy. This calculator returns the total length including waste and the number of sticks rounded up to whole pieces.
Crown molding formula
Total with waste = perimeter * (1 + waste / 100)
Waste length added = total with waste - perimeter
Sticks to buy = ceil(total with waste / stick length)
Crown runs the full perimeter with no openings subtracted. The waste factor covers compound miters and coped joints. Sticks round up to whole pieces.
Crown molding buying tips
- Do not subtract doors or windows; crown runs above them at the ceiling.
- Allow more waste for many corners and for compound or coped cuts.
- Buy longer sticks to minimise joints on long walls.
- Coped inside corners hold tighter than mitered ones as the room moves.
- ICC and HUD residential standards govern interior finish trim in the US.
Crown molding: frequently asked questions
How do I calculate crown molding length?
Add the lengths of all walls to get the ceiling perimeter, then add a waste allowance for inside and outside miter cuts and offcuts. Crown molding runs the full perimeter with no gaps for doors, since it sits at the ceiling.
How much waste should I allow for crown molding?
Crown molding miters are compound cuts and easy to spoil, so many installers allow 10% to 15% waste. Rooms with many corners need more. This calculator lets you set the percentage to match your room and skill.
Do I subtract doors and windows for crown molding?
No. Crown molding runs continuously along the top of the wall at the ceiling, above doors and windows, so you do not subtract any openings. This is the main difference from baseboard.
How many sticks of crown molding do I need?
Divide the total length including waste by the length of one stick, commonly 8 feet, and round up to whole sticks. Buying full lengths reduces the number of joints on long walls.
Why are crown molding cuts harder than baseboard?
Crown sits at an angle between wall and ceiling, so corners require compound miter or coped cuts. The higher difficulty is why a larger waste allowance is sensible for crown than for flat trim.
Official sources
- U.S. Department of Housing and Urban Development: Residential construction guides.
- U.S. General Services Administration: Design and construction standards.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.