📏 Baseboard & Trim Calculator

Enter your room dimensions and door/opening widths to find the linear feet and number of trim boards you need.

Room Length (ft)

Room Width (ft)

Total Door/Opening Width to Subtract (ft)

Standard Trim Board Length (ft)

Waste Allowance (%)

How the board count is worked out

The room is treated as a rectangle, so the wall run is its perimeter. Doorways and cased openings are subtracted as a single total, the waste allowance is added to what is left, and that length is divided by the board length you buy in and rounded up.

perimeter    = 2 x (length + width)
linear feet  = perimeter - openings
with waste   = linear feet x (1 + waste% / 100)
boards       = ceiling(with waste / board length)

The defaults - a 14 x 12 ft room, 6 ft of openings, 12 ft boards, 10% waste - give a 52 ft perimeter, 46 ft of trim, 50.6 ft with waste, and 5 boards.

Why the waste allowance is not optional

Trim is cut at an angle, so almost every joint costs length. Outside corners are mitred at 45 degrees and each one eats roughly the depth of the board twice over; inside corners are usually coped, which means one piece is cut long and then carved back, and a coped joint that splits has to be recut from scratch. On top of that:

Offcuts are rarely reusable. A 2 ft tail from a 12 ft board only helps if you have a wall shorter than 2 ft.
Profiled trim has to be pattern matched at scarf joints, and a warped or knotty length gets rejected on the saw.
Pre-primed MDF chips at the ends during handling.

10% suits a plain room with square corners. Go to 15% for a room with several short walls, and higher again for tall or ornate profiles where a bad cut wastes a lot of expensive stock.

Five 12 ft boards is 60 ft of material for 46 ft of wall, but that surplus is not slack you can spend anywhere. A 14 ft wall cannot be covered by a 12 ft board without a scarf joint, so check your longest wall against the board length before you buy - sometimes 16 ft stock costs less in total than 12 ft stock plus extra joints.

Frequently asked questions

How many linear feet of baseboard for a 12x14 room?

52 ft of wall, less your door openings. Take off about 3 ft per standard door, so one door leaves 49 ft and two leave 46 ft. Add your waste allowance to that figure, not to the raw perimeter.

How much extra baseboard should I buy?

10% for a simple rectangular room, 15% or more once there are alcoves, short returns or a profile that has to be coped. The cuts at corners are what consume it, so the allowance scales with the number of corners rather than with the floor area.

Should I buy 12 ft or 16 ft trim boards?

Buy whatever length covers your longest wall in one piece. A joint in the middle of a long wall is visible in raking light no matter how well it is cut, and the money saved on shorter stock rarely covers the extra filling and sanding.