Baseboard Calculator: Linear Feet & Boards for a Room

Baseboard runs along the bottom of every wall except where a doorway breaks the run, so the amount you need is the room's perimeter minus the door openings. Enter the room length, room width, and the number of doorways — the calculator doubles and adds the length and width to get the perimeter, subtracts about 3 feet for each doorway, adds a waste allowance, and divides by your board length (8-foot boards by default) to tell you how many boards to buy.

Need more control? Open More options to change the assumed door width, switch to metric, adjust the waste percentage, pick a different board length, add matching shoe (quarter-round) molding, or enter a price per linear foot for a quick cost estimate.

Baseboard covers the joint where your walls meet the floor, so you need enough to wrap the whole perimeter of the room — except at doorways, where the trim stops on each side of the opening. That's the one big difference from crown molding: crown runs straight over doorways, while baseboard is broken by them, so you subtract each opening.

The two numbers that matter are linear feet (the total length of trim, including waste) and boards (how many stock lengths you actually carry out of the store). Baseboard is milled in fixed lengths — most commonly 8, 10, 12, or 16 feet — so you almost always buy more total length than the bare wall run. A standard interior doorway is about 3 feet (36 inches) wide, which is the amount this calculator removes per opening by default. If you're also installing shoe molding or quarter-round at the base, you need the same run a second time.

Perimeter = 2 × (length + width)

Net run = perimeter − (doorways × door width)

Linear feet to buy = net run × (1 + waste %)

Boards = linear feet ÷ board length, rounded up

For example, a 12 ft × 10 ft room with 2 doorways has a perimeter of 2 × (12 + 10) = 44 ft. Subtract two 3-foot doorways: 44 − 6 = 38 ft of actual baseboard run. Add a 10% waste allowance: 38 × 1.10 = 41.8 linear feet. With 8-foot boards, 41.8 ÷ 8 = 5.23, which rounds up to 6 boards. Always round boards up — you can't buy a fraction of a board.

How much baseboard for a 12x12 room with 2 doors? Perimeter = 2 × (12 + 12) = 48 ft, minus 6 ft for doorways = 42 ft. With 10% waste that's 46.2 linear feet, or 6 eight-foot boards.

A small 10x10 bedroom with one door: perimeter = 40 ft, minus 3 ft = 37 ft, +10% = 40.7 linear feet = 6 boards of 8-foot baseboard.

A large 16x20 living room with 3 openings: perimeter = 72 ft, minus 9 ft = 63 ft, +10% = 69.3 linear feet. Using 16-foot boards that's 5 boards; using 8-foot boards it's 9.

- Add 10–15% for waste. Every inside and outside corner needs a mitered or coped cut, and the offcut from one wall rarely starts the next one cleanly.
- Don't over-subtract doorways. Only subtract true openings that reach the floor — cased openings and archways still get baseboard on each return, and closets usually do too.
- Buy the longest boards your walls and vehicle allow. One long board on a long wall means fewer joints and a cleaner look than piecing together short lengths.
- Remember shoe molding. If you're adding quarter-round or shoe at the floor line, you need the same linear footage a second time — turn that option on.
- Keep the offcuts for short runs beside doorways and inside closets, and buy it all from one batch so the profile matches.