Key takeaways
- Baseboard needed = room perimeter − door openings.
- Longer pieces mean fewer joints, as long as they can reach the room.
- Old trim in a pre-1978 home may have lead paint, so check before you remove or sand it.
Enter the room's size, total door width and the stock length you plan to buy. You can run this for each room and add the results.
How the calculator works
- Baseboard: 2 × (length + width) − door openings
- Order: baseboard × (1 + waste %)
- Pieces: order ÷ stock length, rounded up
The 10% default is our planning figure rather than a published standard. A room with many corners or short runs can use more.
Worked example
A 12 × 15 foot room with one 3-foot door, using 16-foot pieces:
- 2 × 27 − 3 = 51 feet
- With 10% waste: 56.1 feet
- 56.1 ÷ 16 = 3.5, so 4 pieces
How stock length changes your order
| Stock length | Pieces for 56.1 ft | Feet you'd buy |
|---|---|---|
| 8 ft | 8 | 64 |
| 12 ft | 5 | 60 |
| 14 ft | 5 | 70 |
| 16 ft | 4 | 64 |
The math is only part of it. Long pieces mean fewer joints, but check that they fit in your vehicle and up the stairs.
Plan it by wall
The total can hide a problem. Pieces have to fit each wall, and offcuts only help if they're long enough to use. So sketch the room:
- Short walls: can they use offcuts from longer ones?
- Long walls: do they need a joint, and can it go somewhere less visible?
- Other trim: add closets, and any window or door casing separately.
Old homes
In a home built before 1978, old painted trim may contain lead. EPA's RRP rule covers paid work that disturbs paint in these homes, and the dust matters whoever makes it. Read about lead paint before you pry, sand or scrape.
Frequently asked questions
How much baseboard do I need for a 12 × 12 room?
The perimeter is 48 feet, less your door openings, and then add your waste allowance.
Do I subtract door openings?
Yes, unless the trim continues across them. Subtract the width of each opening.
How much extra should I buy?
There's no standard figure we can cite. We default to 10%, and complex rooms can need more.
Sources
We use primary sources where we can: building codes, federal rules and manufacturer documents. Read our editorial standards.