Baseboard runs around the room's perimeter minus the door openings. A 12 × 14 ft room with one door needs 49 linear feet (52 feet of wall less about 3 feet for the door and its casing), which the calculator cuts from one 16 ft and three 12 ft lengths, plus one spare 8 ft length for a 10% waste allowance.
How the baseboard is calculated
Linear feet = 2 × (length + width) − doors × door opening
The door opening is the door plus its casing on both sides: a 32 inch door with 2¼ inch casing and a 3/16 inch reveal each side spans about 36¾ inches, so the default takes 36 inches per door. Change it for wider doors or when a door's casing sits a few inches from a corner.
Then the calculator works out real pieces, not just footage. Each wall becomes a run; the door comes out of the longest wall, which it splits in two. Runs longer than the longest length you buy get a joint. All runs are then packed into the lengths you chose, longest first, so the offcut of one wall can finish a short wall. The cutting diagram shows every length with its pieces and what is left over.
Worked example: a 12 × 14 ft bedroom
- Perimeter: 2 × (14 + 12) = 52 ft.
- One door: 52 − 3 = 49 linear feet, in five runs: 14, 12, 12 and two 5½ ft pieces either side of the door.
- Buying 8, 12 and 16 ft lengths: the 14 ft wall comes from a 16, each 12 ft wall from a 12, and the two door-side pieces share the third 12. That is four lengths, 52 feet.
- 10% waste on 52 feet is 5.2 feet, so one more 8 ft length for a cope that goes wrong.
- Nails: two at every stud (16 inches on center) along each run, 82 finish nails.
- Four inside corners to cope, no outside corners, no joints on any wall.
These are the calculator's defaults. Try 16 ft only and you get four 16s for the same room, with longer offcuts.
Baseboard for common room sizes
| Room | Perimeter | Less one door | With 10% waste |
|---|---|---|---|
| 10 × 10 ft | 40 ft | 37 ft | 40.7 ft |
| 10 × 12 ft | 44 ft | 41 ft | 45.1 ft |
| 12 × 12 ft | 48 ft | 45 ft | 49.5 ft |
| 12 × 14 ft | 52 ft | 49 ft | 53.9 ft |
| 12 × 16 ft | 56 ft | 53 ft | 58.3 ft |
| 14 × 16 ft | 60 ft | 57 ft | 62.7 ft |
| 16 × 20 ft | 72 ft | 69 ft | 75.9 ft |
This Old House gives the same rule of thumb for buying: measure the room and add 10% for waste.
Joints and corners
Where a wall is longer than your longest length, two pieces meet in a scarf joint: This Old House cuts both ends at opposing 45° angles, overlaps them and secures them with wood glue and finish nails. The calculator counts one joint per extra piece on a wall and marks it in the room plan.
Inside corners are usually coped: one piece runs into the corner square, the other is cut to the profile of the first. This Old House says coping typically produces the best results. Outside corners are two 45° miters, dry-fitted and glued; for walls that are not square, the miter angle calculator gives the angle for any corner. A plain rectangle has four inside corners; add one inside and one outside corner for each wall that steps in or out.
Nails and caulk
This Old House fastens baseboard with 8d finish nails driven at a slight downward angle near the top and bottom edges: the top into the studs, the bottom into the wall's bottom plate. That is two nails per stud, and the calculator counts the studs along each run from the stud spacing you enter. Family Handyman's guide uses 6d finish nails into the studs and 4d for base cap and shoe molding; either way, the count is the same.
A bead of caulk along the top edge, where the base meets the wall, closes the gap before paint. The bead is as long as the baseboard; the caulk calculator turns that length into tubes.
Cost
Baseboard is priced by the linear foot or by the piece. Enter a price per linear foot and the calculator multiplies it by the length you actually buy, spares included, not just the wall length.
What to work out next
- Door and window casing, crown and shoe molding for the same room: the trim calculator.
- The floor under it: the flooring calculator, since new flooring is the usual reason for new base.
- Painting the walls above it: the paint calculator.
More finish tools are under floors, tile and trim.