About this calculator
Baseboard and other trim is sold by the piece in fixed lengths, but rooms come in walls, and a piece of trim can’t be split across two walls without a joint. That’s why simple linear-foot math often comes up a piece short. This calculator does both: it finds the room’s perimeter less the doorways and adds an allowance for cuts, and it also lays out a cut list, wall by wall, saying which wall comes out of which piece and what’s left over.
You buy whichever count is higher, so you have enough to give every wall shorter than a piece one continuous length, and a spare for the cut that goes wrong. 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, measured along the walls at floor level.
- Enter the number of doorways and their width including the casing, since baseboard stops at the door casing.
- Choose the piece length your store sells. Longer pieces mean fewer joints on long walls; shorter ones fit in a car.
- Keep 10% extra for miters, copes and the occasional bad cut, and add your price per foot to see the cost. Take the cut list to the store and to the miter saw.
The formula
Perimeter = 2 × (length + width)
Trim length = perimeter − doorways × doorway width
Pieces by length = trim length × (1 + extra%) ÷ piece length, rounded up
Pieces by cut list = wall pieces packed into stock pieces (⅛ in per saw cut)
Pieces to buy = the larger of the two
For the cut list, each wall’s trim is one piece when it fits in one stock length. A longer wall gets full pieces joined end to end, and the last piece is kept at least 2 ft long so it always reaches a stud (studs are 16 in apart in most US walls). The wall pieces are then packed into stock pieces longest first, so the offcuts from short walls are reused where they fit. Doorways shorten walls 1, 2, 3 and 4 in turn. The cut list treats what’s left of a wall as one run, which is the cautious case: if the door is near a corner, the short return beside it usually comes out of an offcut.
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 % |
| Trim, per foot | $1.25 |
| Bought | Item | Buy | Cost |
|---|---|---|---|
| Piece 1: wall 3 (14')Offcut 2', for closets and returns | 1 × 16 ft | $20.00 | |
| Piece 2: wall 2 (12')Offcut 4', for closets and returns | 1 × 16 ft | $20.00 | |
| Piece 3: wall 4 (12')Offcut 4', for closets and returns | 1 × 16 ft | $20.00 | |
| Piece 4: wall 1 (11')Offcut 5', for closets and returns | 1 × 16 ft | $20.00 | |
| Trim cost | $80.00 | ||
Tips before you buy
- Buy pieces at least as long as your longest wall where you can. A continuous run looks best, and the cut list shows how few joints you can get away with.
- Where you must join two pieces, use a 45° scarf joint over a stud rather than a butt joint, and glue the joint as well as nailing it.
- Coping inside corners gives tighter joints than mitering, especially on walls that aren’t square. Miter the outside corners.
- Cut each piece a hair long and test-fit it before nailing. You can trim it shorter, but not longer.
- Prime and paint trim before installing it; you’ll only need to fill nail holes, caulk the top edge 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 many pieces of baseboard do I need for a 12×14 room?
With one 3 ft doorway, you need 49 linear feet; adding 10% gives about 54 ft. That’s four 16 ft pieces (one per wall, no joints) or five 12 ft pieces, because one 14 ft wall needs a 12 ft piece plus a 2 ft piece joined to it.
Why does the cut list sometimes need more pieces than linear feet?
Linear-foot math assumes every scrap can be used anywhere. Take a 9 × 9 ft room with no doorway and 16 ft pieces: 36 ft plus 10% is 39.6 ft, about three pieces. But a 16 ft piece gives only one 9 ft wall (the 7 ft offcut is too short for another), so it takes four pieces to trim every wall without a joint.
How much extra baseboard should I buy?
Add 10% for cuts and joints. For rooms with many short walls or outside corners, add 15%. The calculator also checks the cut list and adds spare pieces only when the cut list leaves less than your extra.
Do I need baseboard in closets?
Usually yes, if the closet has a finished floor. Closet walls are short, so they’re a good use for the offcuts the cut list shows; if there aren’t enough, measure the closet as its own room.
Sources
Areas and volumes are standard geometry. The published figures this calculator relies on come from these sources; other defaults (waste allowances, typical densities and prices) are common trade figures worth checking with your supplier.
- International Residential Code 2021, Chapter 6 (R602.3, stud spacing): studs 16 in apart, so an end piece of 2 ft or more always crosses a stud to nail into