Baseboard & Trim Calculator: How Much Do I Need?
Calculate the linear feet of baseboard, crown molding or other trim for a room, and how many stock-length pieces to buy.
Baseboard length equals the room perimeter minus doorways: a 12 × 12 ft room has 48 ft, or about 45 ft with one 3-ft doorway, so roughly 50 ft with 10% waste. That is seven 8-foot pieces. Do not subtract doorways for crown molding.
Your numbers
Result
How to calculate baseboard
Baseboard runs along the bottom of every wall, so its length is the room's perimeter minus the width of any doorways.
pieces = linear feet × (1 + waste %) ÷ stock length (round up)
Add 10% for miter cuts, mistakes and splices. For rooms with many corners, bump that to 15%. Crown molding, chair rail and shoe molding use the same math; for crown molding don't subtract doors.
Baseboard needed by room size
| Room size | Perimeter | Net (1 doorway) | 8-ft pieces (+10%) |
|---|---|---|---|
| 10 × 10 ft | 40 ft | 37 ft | 6 |
| 10 × 12 ft | 44 ft | 41 ft | 6 |
| 12 × 12 ft | 48 ft | 45 ft | 7 |
| 12 × 14 ft | 52 ft | 49 ft | 7 |
| 14 × 16 ft | 60 ft | 57 ft | 8 |
| 16 × 20 ft | 72 ft | 69 ft | 10 |
Choosing stock length
Buying 12- or 16-foot lengths helps avoid joints on long walls, but they're harder to transport. Plan your cuts so that joints land on studs, and cut joints at 45° (scarf) so they stay tight as the wood moves.
Trim types
| Trim | Typical height | Where |
|---|---|---|
| Baseboard | 3¼–5¼ in | Bottom of walls |
| Shoe / quarter round | ¾ in | On the floor, against baseboard |
| Crown molding | 3–6 in | Where wall meets ceiling |
| Chair rail | 2–3 in | About 32–36 in above the floor |
Pair this with the flooring calculator and paint calculator for a complete room makeover.
Frequently asked questions
How much baseboard do I need for a 12×12 room?
The perimeter is 48 feet. With one 3-foot doorway you need 45 feet, or about 50 feet with 10% waste — seven 8-foot pieces.
How do I calculate crown molding?
Use the full room perimeter without subtracting doorways, then add 10–15% for corners and waste.
Do I include closets?
Yes. Add the wall length inside each closet that will get trim.
How much extra trim should I buy?
Ten percent is standard; 15% if you have lots of corners or you're new to trim carpentry.
What's the difference between baseboard and shoe molding?
Baseboard covers the gap between wall and floor; shoe molding is a thin strip on top of the floor that hides irregularities. Calculate each separately.
How many linear feet is a 10×10 room?
The perimeter is 40 linear feet; with one doorway deducted about 37 feet.
Should baseboard be installed before or after flooring?
Install baseboard before flooring when possible, then add shoe molding after to cover the expansion gap.
How do I join baseboard on a long wall?
Cut matching 45° scarf joints over a stud and glue them, rather than butting square ends.
Related calculators
. Estimates only. Always confirm quantities with your supplier or a qualified contractor before ordering, and add extra for waste and site conditions.