Enter the room size, how many rooms are the same, and the door openings. The calculator works out the linear feet of trim, adds a waste allowance for cuts and joints, and converts it to whole pieces.
Baseboard & trim calculator
How it works
- Perimeter = 2 × (length + width)
- Net length = (perimeter − door openings) × rooms (crown and chair rail run the full perimeter)
- To buy = net length × (1 + waste %)
- Pieces = length to buy ÷ piece length, rounded up
Worked example
A 14 × 12 ft room with one 36 in door opening, using 16 ft baseboard:
- Trim: Baseboard or shoe (skip door openings)
- Room length: 14 ft
- Room width: 12 ft
- Number of rooms this size: 1
- Door openings per room: 1
- Width of each door opening: 36 in
- Piece length: 16 ft
- Waste for cuts and joints: 10%
- Price per linear foot (optional): $0
The calculator gives:
- Pieces to buy: 4 pieces, 16 ft long
- Linear feet with waste: 53.9 ft
- Net linear feet: 49.0 ft
The perimeter is 52 ft, less 3 ft for the door, 49 ft. With 10% for cuts that is 53.9 ft, so four 16 ft pieces.
Material and waste notes
- Every inside and outside corner uses a little extra length for the cope or miter. Rooms with bump-outs, closets and angled walls need a bigger allowance.
- Longer pieces mean fewer joints. Buy lengths that span your longest walls if you can.
- Measure closets separately if they get baseboard too.
- The waste allowance is your choice, not a published standard.
Frequently asked questions
How much baseboard do I need for a 12 x 12 room?
The perimeter is 48 ft. Less one 3 ft door, 45 ft, or 49.5 ft with 10% extra: five 12 ft pieces or four 16 ft pieces.
Do you subtract doorways for baseboard?
Yes, baseboard stops at the door casing. Crown molding and chair rail usually run the whole perimeter.
Is baseboard sold by the linear foot?
Usually by the piece in 8, 12 or 16 ft lengths, often priced per linear foot. Enter the price per foot to see the cost.
Sources
Last reviewed: 25 September 2026. The calculation is covered by automated tests with known answers taken from the sources above. Found an error? Please let us know.