# 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.

**Quick answer:** 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.

_Last updated: October 3, 2026. Estimates only; confirm quantities with your supplier._

## 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.

```
linear feet = 2 × (length + width) − doorway widths
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](../flooring-calculator/) and [paint calculator](../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.