Baseboard / Trim Calculator
Work out exactly how many trim pieces you need for a room, with the standard miter-cut waste allowance already built in. Add your own prices for a full cost estimate — nothing here uses a stale national average.
How this calculator works
The calculator subtracts door and opening widths from the room perimeter, adds a 10% allowance for miter cuts at corners, then rounds up to whole pieces at your chosen board length:
linear_ft_needed = perimeter − sum(door_widths) pieces = ceil( (linear_ft_needed × 1.10) / piece_length )
Door and opening widths come off the total because baseboard doesn't run across an open doorway — only the wall sections on either side get trim.
Worked example
A 12 ft × 14 ft room with one 32 in door, using 12 ft trim pieces:
- Perimeter: 2 × (12 + 14) = 52 ft.
- Door width: 32 in ÷ 12 ≈ 2.67 ft subtracted.
- Linear ft needed: 52 − 2.67 = 49.33 ft.
- With 10% waste: 49.33 × 1.10 ≈ 54.27 ft.
- Pieces: ceil(54.27 ÷ 12) = 5 pieces of 12 ft trim.
At $18 per piece plus four corner blocks at $3.50 each, that example totals 5 × $18 + 4 × $3.50 = $104.
Corners and waste
| Situation | Guidance | Why |
|---|---|---|
| Simple rectangular room | 10% | Four corners, minimal offcut waste |
| L-shaped or bump-out room | 12–15% | More outside corners waste more per cut |
| Quarter round / shoe molding | Calculate separately | Same perimeter, different piece lengths and price |
For rooms with several outside corners, bump the waste allowance up rather than relying on the default 10% — enter a shorter perimeter buffer isn't necessary, just plan on an extra piece if the math comes out close to a round number.
Measuring your room
The same formula works for any room shape — only how you enter the perimeter changes:
- Rectangular rooms — use direct entry with 2 × (length + width), or list each wall.
- Irregular rooms — switch to wall-by-wall and add one entry per wall segment.
- Closets and alcoves — include their perimeter too; baseboard usually continues inside.
- Door and opening widths — measure the rough opening, not just the door slab.
How much does new baseboard cost?
Rather than quoting a national average that's stale the day it's published, this calculator prices the job from what you actually enter. Choose Per piece if your supplier sells fixed 8, 12 or 16 ft boards, or Per linear ft if they cut to length from stock. Add an optional corner block count and price if your install uses them instead of mitered corners. The estimate doesn't include paint, caulk, nails, or removal of existing trim.
Frequently asked questions
How much extra should I buy for corner cuts?
A standard 10% allowance on top of linear footage covers material lost to miter cuts at inside and outside corners, plus the odd re-cut. Rooms with lots of jogs, closets or bump-outs can run closer to 15%.
Inside vs outside corners — does the waste differ?
Outside corners generally waste a bit more than inside corners, since the outward miter trims more off the board's face. A standard 10% allowance covers a typical mix of both; rooms with several outside corners should round up toward 15%.
Should quarter round be calculated separately?
Yes. Quarter round or shoe molding runs along the same perimeter but is a different profile, sold in its own piece lengths and priced separately — run it through this calculator as its own pass using the same perimeter and door widths.
What's a typical baseboard height for standard vs tall ceilings?
3 to 3.5 inch baseboard is standard for 8 ft ceilings. Rooms with 9 to 10 ft or taller ceilings usually move up to 5 to 7 inch baseboard. Height changes material and price per foot, not the linear footage calculation, which is driven entirely by perimeter.