Crown Molding Calculator
Find linear feet of crown molding for a room.
Default 10%
Results update as you type.
How it works
Crown molding decorates the joint between walls and ceiling, and this calculator finds how much you need from the room's dimensions. You enter the room length and width and a waste allowance, and it returns the linear feet of molding and the number of standard eight-foot pieces to buy. Because crown molding runs continuously around the entire top perimeter of the room, the estimate is based on the perimeter, twice the length plus twice the width, with nothing subtracted for doors or windows since the molding passes above them uninterrupted. A waste allowance is especially important for crown molding because its compound miter and cope cuts at corners are unforgiving; a botched cut wastes a length, and matching a later purchase can be difficult. Ten percent is a reasonable default, but for rooms with many corners or for less experienced installers, fifteen percent gives valuable breathing room. Crown molding is sold in fixed lengths, commonly eight feet, so converting linear feet into whole pieces tells you what to actually order. Longer pieces reduce the number of seams on long walls but are harder to handle and cut. Use this to plan crown molding for living rooms, bedrooms, and formal spaces. Enter your room dimensions to compute the crown molding needed.
Linear feet = perimeter × (1 + waste)
Crown molding runs the full perimeter of the ceiling, so the calculator takes twice the room length plus twice the width and multiplies by one plus the waste fraction. Dividing by eight feet and rounding up gives the number of standard pieces. No openings are subtracted, since crown molding is continuous around the top of the walls.
Source:Trim estimation
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter room length and room width.
- 2
Adjust the options
Adjust waste allowance if they apply — sensible defaults are already set.
- 3
Read your result
Crown molding needed updates instantly as you type — no button to press.
Frequently asked questions
How do I calculate crown molding for a room?
Add twice the room length and twice the width to get the ceiling perimeter, then add a waste allowance for corner cuts. Divide by the length of your molding stock to find the number of pieces. Crown molding runs continuously, so unlike baseboard you do not subtract for doors or windows.
Why not subtract doors and windows?
Crown molding is installed at the top of the walls, where they meet the ceiling, so it passes above doors and windows without interruption. Openings only affect trim at floor level, like baseboard. Therefore the full room perimeter is used for crown molding, with no deductions for doors or windows.
How much extra should I buy?
At least ten percent extra is wise, and fifteen percent is safer for rooms with many corners or for do-it-yourself installers. Crown molding requires precise compound miter or coped cuts, and a mistake ruins a length. Extra material also lets you match the profile and finish if you need to replace a damaged piece later.
What size crown molding should I choose?
Crown molding size is usually scaled to ceiling height: taller ceilings suit wider molding. A common guideline is a molding roughly half an inch of height for each foot of ceiling height, so a nine-foot ceiling pairs well with molding around four to five inches. This calculator estimates length regardless of the profile width you pick.
Should I buy longer pieces?
Longer pieces, such as twelve or sixteen feet, reduce the number of seams on long walls, giving a cleaner look, but they are harder to transport, handle, and cut, especially crown molding held at an angle. Eight-foot pieces, the default here, are easiest to work with. Choose based on your wall lengths and installation skill.