Baseboard Calculator
Enter your room size and how many door openings it has. You'll get the baseboard needed in linear feet and in pieces of your chosen length, with a waste allowance for miter and scarf cuts.
Results
How the baseboard calculator works
Baseboard runs around the perimeter of the room, so the calculator adds up all four walls, subtracts the door openings (which get no baseboard), and adds 10% for the miter and scarf cuts that shorten every usable piece.
Formula: (2 × (length + width) − door openings) × 1.10 = linear feet, then ÷ trim length = pieces
| Room | Perimeter | Linear ft to buy |
|---|---|---|
| 10 × 10 ft | 40 ft | ≈ 41 ft |
| 12 × 14 ft | 52 ft | ≈ 54 ft |
| 15 × 20 ft | 70 ft | ≈ 74 ft |
Trim-buying tips
- Cope inside corners rather than mitering them — a coped joint stays tight even if the walls aren't perfectly square, which they never are.
- Buy the longest pieces that fit your walls in one run; splicing mid-wall with a scarf joint is more work and shows.
- Order all your trim from the same batch so the profile and colour match, and let it sit in the room a couple of days to acclimate before cutting.
- Buying pre-primed trim saves a coat of paint and a lot of masking later.
Frequently asked questions
How do I calculate how much baseboard I need?
Add up the room's perimeter — two times length plus width — subtract the width of each door opening, then add about 10% for miter cuts and waste. Divide by the length of trim you're buying to get the number of pieces.
How much baseboard for a 12x12 room?
A 12 × 12 room has a 48 ft perimeter. Subtract one 3 ft door and add 10% waste and you need about 50 linear feet — four 16-foot pieces.
Should I subtract doorways for baseboard?
Yes. Door openings get no baseboard, so subtract each opening's width — usually about 3 feet — from the perimeter. Windows that run to the floor and cased openings come off too; standard windows above the floor do not.
How much extra baseboard should I buy?
About 10%. Every miter and scarf cut shortens a piece, coped inside corners waste a little, and boards occasionally split or arrive damaged — the allowance keeps you from a second trip mid-install.