Trim & Baseboard Linear Feet Calculator
Trim, baseboard and casing are priced and painted by the linear foot, not the square foot. Take the run around the room, subtract the door openings, and add a waste allowance for miters and offcuts.
A run of 54 ft less 3 ft of door openings is 51.0 lf, or 56.1 lf with 10% for miters and waste. Trim, baseboard and casing are measured (and often priced) by the linear foot — take the run length and add ~10%.
Calculator inputs
Walls are area; trim is length. Baseboard, door and window casing, crown and chair rail are all measured in linear feet — and painted in a separate, harder enamel in a different sheen. Getting the linear footage right tells you how much trim enamel to buy (a little goes a long way) and lets you sanity-check a painter who prices trim by the foot.
The room perimeter is a solid starting point for the baseboard run; subtract the door openings, then add a waste allowance for the mitered corners and the inevitable offcuts.
Formula
trim linear feet = (run − door widths) × (1 + waste)
Waste is a fraction — 0.10 adds 10%. For crown, casing or chair rail, add each of those runs into the total the same way.
Worked example
A room with a 54 ft perimeter, one 3 ft door, 10% waste:
- Run − door = 54 − 3 = 51 lf.
- With waste = 51 × 1.10 = 56.1 linear feet.
A single quart of trim enamel typically covers a lot of linear feet, so you are usually buying by the run length, not the area — measure the run, add the waste, and round to a whole can.
Measure the run, add for miters
Trim is fiddly — measure it deliberately:
- Count only real runs. No baseboard crosses a doorway; deduct each door width. Cased openings without a door still get casing, though.
- Add the other profiles. Crown, casing and chair rail each have their own run — total them in.
- Miters waste stock. 45° corners and coped joints produce offcuts; 5–10% waste is normal, more for a room full of short walls.
- Buy enamel by coverage, not guesswork. Trim enamel is sold by area coverage — for a rough paint figure, trim is a narrow band, so a quart or two usually covers a room.
Frequently asked questions
How do I measure baseboard for a room?
Take the room perimeter as the run, subtract the width of each door opening, and add ~10% for miters and offcuts. A 54 ft perimeter with one 3 ft door works out to about 56 linear feet.
Why linear feet and not square feet?
Trim is a narrow, consistent profile, so its length is what matters — for both how much stock you buy and how painters price it. A gallon of enamel covers a huge run of trim, so the square-foot area is almost beside the point.
How much waste should I add?
5–10% is typical. Lean toward 10% (or more) in rooms with many short walls, lots of corners, or complex casing, where mitered offcuts add up.