Calculate baseboard, casing, or crown molding linear feet for a room.
Shopping list
Estimated cost
Usage Tip
Buy molding in the longest lengths that fit your walls to minimize seams, and cut scarf joints where you must join pieces.
The result is total linear feet to buy.
How much baseboard or trim do I need?
Measure the perimeter of the room, subtract the door openings, add a waste factor for miter cuts and mistakes, then divide by the length of the stock you are buying and round up to whole sticks. That last step is the one most calculators skip and the one that saves the 8:47 Sunday-night trip: this tool tells you to buy, say, five 12-foot sticks, not just that you need 54 linear feet.
How to calculate room perimeter for trim
For a rectangular room the perimeter is two times the length plus the width: a 12 by 14 ft room is 2 x (12 + 14) = 52 ft. Subtract each door opening, since baseboard stops at the casing. Windows usually do not interrupt baseboard, but they do break a chair rail or picture rail, so those get deducted too. This calculator handles the deductions automatically based on the trim type.
Standard trim lengths
Trim and molding are sold in standard stock lengths. Longer sticks mean fewer joints on long walls but are harder to handle and transport.
| Stock length | Good for |
|---|---|
| 8 ft | Short walls, closets, easy transport |
| 10 ft | Common rooms, balance of yield and handling |
| 12 ft | Most rooms; fewer joints |
| 14 ft | Long walls with minimal seams |
| 16 ft | Great rooms; needs a truck and a helper |
Trim waste percentage
Every mitered corner and coped joint wastes a little material, and a miscut wastes a lot. Add a waste factor on top of the net length:
| Trim | Suggested waste |
|---|---|
| Baseboard, chair rail, shoe | 10 percent |
| Crown molding | 15 percent (compound miters) |
| Simple straight runs | 5 percent |
Crown molding earns the higher number honestly; the compound miters seem designed in part to test human patience.
Crown molding calculator guide
Crown is measured the same way as baseboard — perimeter around the room at the ceiling — but it cuts at a compound angle, so corners eat more material and mistakes are common. Use 15 percent waste, buy a couple of extra feet for setup test cuts, and cope inside corners rather than mitering them for a tighter fit.
Trim material recommendations
| Application | Recommended trim |
|---|---|
| Living room / bedroom | MDF baseboard, paint grade |
| Bathroom / laundry | PVC trim, moisture-proof |
| Exterior | PVC or composite |
| High-end / stain grade | Poplar, oak or maple |
| Budget straight runs | Finger-joint pine, paint grade |
Frequently asked questions
Do I subtract doors when calculating baseboard?
Yes. Baseboard stops at each door casing, so subtract the width of every door opening from the perimeter.
Do I subtract windows?
Not for baseboard, since it runs under the window. For chair rail or picture rail, which sit at window height, subtract the window widths.
How much waste should I add for trim?
About 10 percent for most trim and 15 percent for crown molding. Use 5 percent only for simple straight runs with few corners.
What length trim should I buy?
Longer sticks mean fewer joints on long walls. Twelve foot is a good default; match the stock length to your longest walls where you can.
How many pieces of baseboard do I need?
Take the net length with waste and divide by the stock length, then round up. The calculator does this and gives a piece count to buy.
What trim is best for bathrooms?
PVC trim, because it will not swell or rot with moisture. MDF and bare wood are poor choices in wet rooms.
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Coming soon: Paint Calculator · Crown Molding Calculator · Baseboard Calculator
Estimates are for planning. Actual needs vary with wall layout, joint method, returns and pattern matching; measure each wall, confirm your longest runs against the stock length, and buy a little extra for setup cuts and mistakes.