How this calculator works
The room perimeter minus doorway widths gives the linear feet of trim. A waste allowance covers miters and short offcuts, and the total is divided by the piece length and rounded up.
Linear ft = 2 × (Length + Width) − Doorways × Width ÷ 12
Pieces = round up( Linear ft × (1 + Waste%/100) ÷ Piece length )
Assumptions and tips
- Longer pieces mean fewer joints along long walls.
- For crown molding, use the same method without subtracting doorways.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Room length | 14 ft |
| Room width | 12 ft |
| Doorways | 1 |
| Doorway width | 36 in |
| Piece length | 16 ft |
| Waste allowance | 10 % |
| Result | Value |
|---|---|
| Pieces to buy | 4 × 16 ft |
| Baseboard needed | 49 linear ft |
| With waste | 53.9 linear ft |
Step by step:
- Perimeter = 2 × (14 + 12) = 52 ft
- Minus doorways = 49 ft; + 10% = 53.9 ft
- Pieces = 53.9 ÷ 16 → 4
Baseboard for common rooms
One 36 in doorway, 10% waste, 16 ft pieces.
| Room | Baseboard needed | Pieces to buy |
|---|---|---|
| 10 × 10 ft | 37 linear ft | 3 × 16 ft |
| 12 × 12 ft | 45 linear ft | 4 × 16 ft |
| 12 × 16 ft | 53 linear ft | 4 × 16 ft |
| 16 × 20 ft | 69 linear ft | 5 × 16 ft |
Common mistakes to avoid
- Buying short pieces for long walls, which forces visible joints.
Frequently asked questions
How much extra baseboard should I buy?
About 10% extra covers miter cuts and mistakes; rooms with many corners need more.