How to use the baseboard calculator
- Measure the room's length and width, or add up the length of every wall that gets baseboard and use "I know the total length".
- Count the doorways, including closets and open archways. Baseboard stops at the door trim.
- Pick the piece length. Longer pieces mean fewer joints on long walls but are harder to carry home; 8 ft fits most cars.
- Use the same numbers for quarter round or shoe molding. For crown molding, leave doorways at 0, since crown runs over them.
Baseboard formula
linear feet = room perimeter − (doorways × doorway width)
to buy = linear feet × (1 + waste)
pieces = to buy ÷ piece length, rounded up
A 10% allowance covers the miter cuts at each corner and a bad cut or two. Rooms with many short walls, like around a fireplace or bay window, use more.
Baseboard for common room sizes
Doorways 3 ft wide with trim, 10% extra.
| Room | Perimeter (ft) | Doorways | Linear ft | To buy (ft) | 8 ft pieces | 16 ft pieces |
|---|---|---|---|---|---|---|
| 10 × 10 ft | 40 | 1 | 37 | 41 | 6 | 3 |
| 10 × 12 ft | 44 | 1 | 41 | 46 | 6 | 3 |
| 12 × 12 ft | 48 | 2 | 42 | 47 | 6 | 3 |
| 12 × 14 ft | 52 | 2 | 46 | 51 | 7 | 4 |
| 14 × 16 ft | 60 | 2 | 54 | 60 | 8 | 4 |
| 15 × 20 ft | 70 | 3 | 61 | 68 | 9 | 5 |
| 20 × 20 ft | 80 | 3 | 71 | 79 | 10 | 5 |
Tips for buying baseboard
- Buy pieces longer than your longest wall when you can, so long walls have no joint. Where you must join two pieces, use a 45 degree scarf joint over a stud.
- Inside corners look best coped rather than mitered; outside corners are mitered.
- Primed MDF is the cheapest option for painted trim. Use solid wood or PVC in bathrooms and basements where it may get wet.
- Nails: plan on about one 2 inch finish nail into each stud, or every 16 inches, top and bottom.
Frequently asked questions
How much baseboard do I need for a 12x12 room?
A 12 × 12 room has a 48 ft perimeter. Take out two 3 ft doorways and you have 42 linear ft. With 10% extra, buy about 46 ft: three 16 ft pieces or six 8 ft pieces.
How do you calculate linear feet of baseboard?
Add the length of every wall (or 2 × length + 2 × width for a rectangular room), then subtract the width of each doorway.
How much extra baseboard should I buy?
About 10% for typical rooms and 15% for rooms with many corners. Buy whole pieces, so you usually end up with a little more anyway.
Do you subtract doors when measuring for baseboard?
Yes. Baseboard stops at the door casing, so subtract each doorway, usually about 3 ft including trim. Do not subtract doors for crown molding.