How to calculate baseboard
Baseboard runs along the bottom of every wall except across doorways. The length needed is the room’s perimeter minus the width of the doorways, plus any extra walls such as closets or alcoves. Then add a waste allowance for the miter and cope cuts at the corners, and round up to whole pieces.
Length = 2 × (length + width) − doorways + extra walls
Pieces = length × (1 + waste) ÷ piece length, rounded up
Example
A 14 × 12 ft bedroom with one 3 ft doorway, using 12 ft pieces with 10% waste:
- perimeter: 2 × (14 + 12) = 52 ft;
- minus the doorway: 49 ft of baseboard;
- with waste: 53.9 ft, so 5 pieces of 12 ft;
- at $15 a piece: $75;
- about 74 finish nails, two at every stud (16 in on center).
Choosing the piece length
- Longer pieces (12 or 16 ft) mean fewer joints along a wall, which look better and need less filling. Plan so that each wall gets a single piece where possible.
- Shorter pieces (8 ft) are easier to transport and handle, but long walls will need scarf joints, cut at 45° and glued over a stud.
- Measure each wall and plan which piece goes where: five pieces in total does not help if a 14 ft wall needs one continuous run.
How much waste to allow
- 5 to 10% for simple rectangular rooms;
- 10 to 15% for rooms with many corners, columns or angled walls;
- more if you are new to coping inside corners.
Installation tips
- Inside corners: cope the joint (cut the profile of one piece so it fits over the face of the other) rather than mitering; it stays tight when the wood moves.
- Outside corners: miter at 45° and glue the joint.
- Nail into the studs and the bottom plate with 2 to 2½ in finish nails, using a stud finder to locate them.
- Leave a small gap above the subfloor if you will install carpet, or set the baseboard on the finished floor for hardwood and tile, with quarter-round or shoe molding to cover the expansion gap.
- Let wood baseboard acclimate in the room for a couple of days before installing.
For other rooms, add their perimeters to the “extra wall length” field, or run the calculator once per room.