Calculator
Baseboard & Trim Calculator
Baseboard is bought by the linear foot but sold in fixed board lengths (typically 8, 12, and 16 feet), and the gap between 'linear feet needed' and 'linear feet purchased' is almost entirely down to two things: doorway deductions and miter-cut waste at corners. This calculator starts from room perimeter, subtracts doorway openings, and rounds up to standard stock lengths rather than assuming baseboard comes in exactly the length you need.
For the measuring method including inside/outside corner handling, see how to measure a room for baseboard and trim.
Calculate your quantity
Extra for miter cuts and mistakes.
Baseboard boards
7 8ft boards
- Linear feet needed
- 46 ft
- With waste
- 50.6 ft
Shopping summary
- • 7 x 8ft board(s)
This is an estimate — confirm structural work with a professional.
How this calculation works
Linear footage needed = room perimeter minus the width of each doorway opening (baseboard doesn't run across a doorway threshold). Add a miter-waste allowance — every inside or outside corner requires a 45-degree cut, and cut offcuts from one piece often can't be reused for the next wall's length, so 10% waste on top of net perimeter is a reasonable standard allowance, more on rooms with lots of corners or bump-outs.
Then round up to standard board lengths. If a wall run is 14 feet, you can't buy a 14-foot board — you buy a 16-footer and waste 2 feet, or splice two shorter boards with a scarf joint at a stud location. Planning which wall gets the splice (usually the longest, least-visible run) avoids an obvious seam on a short, high-visibility wall.
Common mistakes
- Ordering exact linear footage with no corner-waste allowance, which comes up short as soon as the first 45-degree cut is made.
- Not planning splice locations ahead of time, resulting in a visible seam on a short prominent wall instead of a long inconspicuous one.
- Forgetting closets — closet perimeter still needs baseboard even though it's easy to overlook when eyeballing a room.
- Buying random board lengths instead of standardizing on 12 or 16-footers, which increases both waste and the number of splices needed.
- Not test-fitting a coped inside-corner joint before committing to the final cut — a coped joint (one board's profile cut to fit over the other) takes practice, and a botched first attempt on the actual stock wastes material that a scrap test cut wouldn't have.
- Painting or finishing baseboard before final installation is confirmed, which can complicate touch-ups if a board needs to be re-cut or swapped.
Shopping summary
Buy standard-length boards (8/12/16 ft) totaling at least net perimeter plus 10% miter waste, favoring longer boards on longer wall runs to minimize splices; add matching outside-corner blocks if your trim style uses them instead of mitered corners.
Worked example: a 12x14 room has a perimeter of 52 feet, minus one 3-foot doorway = 49 feet net. Add 10% miter waste: 49 x 1.1 ≈ 54 linear feet. Buying four 12-foot boards (48 ft) and one 8-foot board (8 ft) covers 56 feet with minimal leftover, better matched to the room's actual wall run lengths than trying to buy the bare 54-foot minimum in odd combinations.
FAQ
Do closets count in baseboard footage?
Yes — closet walls need baseboard just like the main room, and it's a common miss since closets are easy to forget when eyeballing perimeter.
Is 10% enough waste allowance for miter cuts?
For a simple rectangular room, yes; rooms with bay windows, multiple closets, or unusual angles often run closer to 15%, since each additional corner adds another cut that can't always reuse the offcut.
What's the difference between a coped joint and a mitered inside corner?
A mitered inside corner joins two 45-degree cuts, similar to an outside corner but pointing inward, and can open up a visible gap if the wall corner isn't exactly 90 degrees; a coped joint cuts one board's profile to fit directly against the face of the other, which tolerates a slightly out-of-square corner better and is generally preferred by trim carpenters for inside corners specifically.
Should baseboard be installed before or after flooring?
Generally after new flooring is installed, so the baseboard sits on top of and covers the flooring's expansion gap at the wall line — installing baseboard first can mean recutting or shimming it once flooring goes in and changes the finished floor height.
What standard board lengths should I plan around when ordering?
8, 12, and 16-foot lengths are the most commonly stocked at home centers, with some suppliers also carrying 10 and 14-foot boards — favoring the longest board that comfortably covers a given wall run minimizes both waste and the number of splices needed across the room.
Do outside corners need extra board length beyond the wall measurement?
Not extra length exactly, but each outside corner uses more of the board per linear foot of wall than an inside corner does, since the 45-degree miter removes material at an angle rather than a straight butt — this is part of why the standard 10% waste allowance exists rather than ordering exact wall-length totals.