Baseboard Calculator

Work out the linear feet and number of pieces of baseboard or trim you need for a room — with doorways and a waste allowance accounted for — plus the cost.

How to calculate baseboard

Baseboard follows the perimeter of the room, minus the openings:

Linear feet = (perimeter − doorways) × (1 + waste %)

Perimeter is 2 × (length + width). We subtract about 3 feet for each standard doorway, add your waste allowance for cuts and mitered corners, then divide by your trim length to get the number of pieces, rounded up.

Common trim lengths

Piece lengthGood for
8 ftEasy to handle; most rooms
12 ftFewer joints on long walls
16 ftLong, unbroken runs

Tips

  • Plan long walls first. Use full lengths on the longest walls to minimize visible seams.
  • Corners eat material. Mitered inside and outside corners create offcuts — keep the 10% buffer.
  • Buy matching shoe molding if your floors aren't perfectly flat.

Frequently asked questions

How much baseboard for a 12x12 room?
The perimeter is 48 ft. After subtracting one doorway and adding 10% waste, you'll need about 50 linear feet — roughly 7 pieces of 8 ft trim.
How do I work out the number of pieces?
Divide your total linear feet (with waste) by the piece length and round up. Baseboard usually comes in 8, 12, or 16 ft lengths.
Should I subtract doorways?
Yes — about 3 ft per standard doorway, since openings get no baseboard.
How much extra should I buy?
About 10%, more for rooms with lots of corners and miters.

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