How to calculate baseboard
Baseboard is ordered by the linear foot: measure every wall, add them, subtract the width of each doorway and add a cutting allowance. Buy the longest pieces you can handle so that most walls need no splice.
| Room | Perimeter | Baseboard to buy | 16 ft pieces |
|---|---|---|---|
| 10 × 10 ft | 40 ft | 40.7 ft | 3 |
| 12 × 12 ft | 48 ft | 49.5 ft | 4 |
| 12 × 14 ft | 52 ft | 53.9 ft | 4 |
| 14 × 16 ft | 60 ft | 62.7 ft | 4 |
| 16 × 20 ft | 72 ft | 75.9 ft | 5 |
Trim calculator: door and window casing
Casing is counted per opening: two legs plus a head on each side of a door, and four pieces around a window if it has a casing under the stool. The legs run from the floor to the head with a small reveal on the jamb, and the head spans the opening plus both reveals and both casing widths. The calculator totals both rooms of trim; for crown, use the crown molding calculator.
Corners, splices and waste
- Inside corners: cope one piece over the other; a coped joint stays tight when the wall moves.
- Outside corners: miter at 45° for a square corner.
- Splices: join long walls with a scarf (two 45° cuts) over a stud.
- Find the studs with the layout marks from the stud calculator; the wall area for paint or panels is on the wainscoting calculator.
Frequently asked questions
How do I calculate how much baseboard I need?
Add the length of every wall, subtract the doorway widths and add about 10% for cuts. Divide by the piece length to get the number of pieces.
How much baseboard for a 12 × 12 room?
48 ft of wall less a 3 ft doorway is 45 ft; with 10% waste about 49.5 ft, or four 16 ft pieces.
How much casing do I need for a door?
About 17 ft per side of a 36 × 80 in door with 2-1/2 in casing: two 83 in legs and a 42 in head.