Baseboard & Quarter-Round Calculator
Turn a room’s length and width into the linear feet of baseboard or quarter-round you need, less the door openings, then the number of trim pieces to buy.
Calculator
A 12 × 15 ft room has a 54.0 ft perimeter; less 6.0 ft of openings that’s 48.0 lin ft of baseboard or quarter-round — about 6 pieces at 8.0 ft each. Buy a little extra for miter cuts. This is floor-edge trim quantity, not carpentry advice.
Baseboard and quarter-round finish the bottom edge of a wall and hide the perimeter expansion gap a floating floor leaves at every wall. The material is bought by the piece in fixed lengths, so the estimate is a perimeter calculation: measure around the room, subtract the openings that carry no trim, and divide by the length of one piece.
Enter the room’s length and width for a rectangular room; the calculator doubles their sum for the perimeter, subtracts your door and opening widths, and rounds the result up to whole pieces. For an L-shaped or irregular room, add up each wall segment and enter the total as the perimeter equivalent.
Formula
Perimeter, then trim length, then whole pieces:
perimeter = 2 × (length + width)trim_lin_ft = perimeter − door_openingspieces = ceil(trim_lin_ft ÷ piece_length)
Openings without trim — doorways, cased openings, closet fronts — are subtracted from the perimeter. The piece count rounds up because trim is sold whole and you lose length to miter cuts.
Worked example
A 12 × 15 ft room with 6 ft of door openings, in 8 ft lengths:
- perimeter = 2 × (12 + 15) = 54 ft
- trim = 54 − 6 = 48 linear feet
- pieces = ceil(48 ÷ 8) = 6 pieces
Six 8 ft lengths cover the run. Because miters and coped inside corners waste a little, many installers add roughly 10% — here that would round you to seven pieces.
Baseboard vs quarter-round
Baseboard is the taller board against the wall; quarter-round (or a thinner “base shoe”) is the small rounded molding that sits in the corner between the baseboard and the floor, covering the expansion gap and any small floor irregularities. Some jobs use only baseboard, some add quarter-round or shoe over it — run the calculator once per molding you are buying.
Buy about 10% extra for miter cuts, coped corners and the occasional bad length, and match the profile across rooms. This tool gives a floor-edge trim quantity in linear feet — it is not carpentry, painting or wall-trim advice. For the joins between rooms, see the transition strips & trim calculator.
Reference table
Common finished trim lengths and how many cover a run:
| Piece length | Typical use |
|---|---|
| 8 ft (96 in) | Standard baseboard / quarter-round length |
| 12 ft (144 in) | Fewer joints on long walls |
| 14–16 ft | Long profiles, fewer seams |
Add about 10% for miter and coped-corner waste — confirm the exact lengths stocked at your supplier.
Frequently asked questions
What is the difference between baseboard and quarter-round?
Baseboard is the taller trim board fixed to the wall. Quarter-round (or a slimmer base shoe) is the small rounded molding in the corner where the baseboard meets the floor. Quarter-round hides the floor’s expansion gap and follows minor dips in the floor.
How much extra trim should I buy for miter cuts?
About 10% is a common allowance. Inside corners are usually coped and outside corners mitered, both of which waste a little length, and one bad cut on a long wall can cost you a whole piece. Round up and keep an offcut for repairs.
Do I subtract doorways from the perimeter?
Yes — enter the total width of doorways, cased openings and closet fronts that carry no trim in the openings field. The calculator subtracts them from the perimeter so you are not buying trim for gaps in the wall.
What lengths does baseboard trim come in?
8 ft (96 in) is the most common, with 12 ft and longer profiles also stocked for fewer seams on long walls. Enter the length you are buying so the piece count matches your supplier.
Is quarter-round always needed?
Not always. It is common with floating floors to cover the expansion gap neatly, but if the baseboard already sits over the gap or you prefer a cleaner look, you may skip it. Run the calculator only for the moldings you actually plan to buy.