About this calculator
Baseboard and other trim is sold by the piece in fixed lengths, but you need it by the linear foot around the room. This calculator finds the room’s perimeter, subtracts doorways, adds an allowance for miters and scarf joints, and tells you how many pieces to buy.
Use it for baseboard, shoe molding, quarter-round, chair rail and crown molding (set doorways to zero for crown and chair rail that runs across openings).
How to use it
- Enter the room’s length and width.
- Enter the number of doorways and their width — baseboard stops at the door casing.
- Choose the piece length your store sells. Longer pieces mean fewer joints on long walls.
- Keep 10% extra for miters, copes and the occasional bad cut.
The formula
Perimeter = 2 × (length + width)
Trim length = perimeter − doorways × doorway width
Pieces = trim length × (1 + extra%) ÷ piece length, rounded up
This is a linear-foot estimate. For the fewest joints, you can also plan piece by piece: each wall shorter than one piece should get a single, unjointed length.
Worked example
These are the calculator’s starting values and the results they produce:
| Room length | 14 ft |
|---|---|
| Room width | 12 ft |
| Doorways | 1 |
| Doorway width | 3 ft |
| Piece length | 16 ft |
| Extra for cuts | 10 % |
Tips before you buy
- Buy pieces at least as long as your longest wall where you can — a continuous run looks best.
- Where you must join two pieces, use a 45° scarf joint over a stud rather than a butt joint.
- Coping inside corners gives tighter joints than mitering, especially on walls that aren’t square.
- Prime and paint trim before installing it; you’ll only need to fill nail holes and touch up afterward.
Frequently asked questions
How do I calculate linear feet of baseboard?
Add the lengths of all walls (the room’s perimeter) and subtract the width of each doorway. A 12 × 14 ft room has a 52 ft perimeter; minus one 3 ft doorway, that’s 49 linear feet.
How much extra baseboard should I buy?
Add 10% for cuts and joints. For rooms with many short walls or outside corners, add 15%.
How many pieces of baseboard do I need for a 12×14 room?
With one doorway, you need 49 linear feet; adding 10% gives about 54 ft — four 16 ft pieces or five 12 ft pieces.
Do I need baseboard in closets?
Usually yes, if the closet has a finished floor. Measure the closet’s walls and add them to the room total; closet runs are short, so they’re a good use for offcuts from the main room.