Baseboard is bought in pieces of a fixed length, but a room is measured in a continuous run. The purchase is the conversion from one to the other, with an allowance in between.
Net linear run = room perimeter − doorway widths
With allowance = net run × (1 + allowance)
Pieces = with allowance ÷ stock piece length, rounded up
A 14 × 12 ft room
The perimeter is 52 ft. The baseboard stops at the doorways, and 6 ft of doorways comes off, leaving 46 ft. With the 10% allowance that is 50.6 ft. Dividing by an 8 ft piece gives 6.33 pieces before rounding, so the list says 7 × 8 ft pieces.
This example assumes
- A 14 × 12 ft room with 6 ft of doorways in total
- 8 ft pieces, which is an example: use the length of the trim you will buy
- 10% allowance for corners, miters and defects, an editable planning default
Worked example 14 × 12 ft room, 6 ft of doorways, 8 ft pieces
| Material | Calculated | Buy |
|---|---|---|
| Baseboard8 ft pieces, 10% extra | 6.33 pieces (estimated) | 7 × 8 ft pieces |
Linear feet are not pieces
The room needs 46 ft of baseboard, but the planner reports 7 × 8 ft pieces: whole pieces, with a little extra at the end of the last one. The same room with different piece lengths:
| Piece length | Estimated pieces | Pieces to buy |
|---|---|---|
| 8 ft | 6.33 | 7 × 8 ft pieces |
| 10 ft | 5.06 | 6 × 10 ft pieces |
| 12 ft | 4.22 | 5 × 12 ft pieces |
Longer pieces mean fewer joints, and which length is best depends on your walls and what you can buy.
An estimate, not a cut plan
The count divides the total run by the piece length. Real cutting depends on where the corners and doorways fall, the miter and scarf joints, defects and whether you reuse the offcut from one wall on another. Those can change the real number, which is why the planner calls the result estimated pieces and keeps the allowance editable.
Where the perimeter comes from
If you are unsure how to get the run, including odd-shaped rooms and several rooms, see how to measure baseboard in linear feet. The measuring habits in how to measure a room apply here too, and flooring that goes in the same room is covered by how much flooring you need.
What changes the estimate?
- The doorway and opening widths the trim stops at
- The piece length you buy
- The allowance for corners, miters and defects
- Whether you are trimming one room or several