Baseboard Calculator

Enter room sizes or wall lengths, take off the doorways and see the linear feet and the pieces to buy.

Room 1

Length

Width

Doorways and openings

Optional. Where the baseboard stops, like a door or an archway.

Opening 1

Width

How many

Extra to add (%)

Optional. For corners and waste. Empty means 0.

How to calculate how much baseboard you need

Baseboard is sold by length, so you need the linear feet of wall that will get trim, not the floor area. Measure the walls, take off the openings, and then see how many pieces cover that length.

Step	Formula
1. Walls	Rectangular room: 2 × (length + width). Or add each wall
2. Take off openings	Subtract the width of each doorway or opening
3. Add extra	Length × (1 + extra ÷ 100)
4. Pieces	Length ÷ piece length, rounded up

In “Rooms” you type each rectangular room and the calculator adds the four walls. In “Wall runs” you type each stretch of wall by itself, which suits rooms with bays or odd shapes. You can enter feet, inches, yards or meters, or a tape-measure reading like 10'6" or 10 ft 6 in.

What lengths does baseboard come in?

The pieces in the result use four lengths. They come from the product pages of Alexandria Moulding, a moulding manufacturer, which we checked in October 2026: 8 foot (a primed MDF bevel baseboard), 12 foot, 14 foot and 16 foot. A profile is made in some of these lengths and not in all of them. On the page of one of its step baseboards, for example, the 14 and 16 foot lengths are shown as unavailable. Check the lengths of the profile you pick, and read the number for that length in the table.

Minimum pieces and wall by wall

The result shows two counts for each length. Minimum divides the total length by the piece length, which only works if you can use every offcut. Wall by wall counts the pieces each wall needs on its own, rounding up on every wall, so it is what you buy if offcuts do not carry from one wall to the next. It does not subtract openings, so treat it as a high estimate. The real number lies between the two. Longer pieces mean fewer joints on a wall, but a long piece is harder to carry and to fit, which is a choice for you and your installer.

Example: a 12 ft by 10 ft room with two doorways

The room is 12 feet by 10 feet. It has two doorways of 3 feet each and you want 10% extra. Enter one opening of 3 feet with a count of 2 to get the same result in the calculator.

Step	Operation	Result
Walls	2 × (12 + 10)	44 ft
Openings	2 × 3	6 ft
Baseboard length	44 − 6	38 ft
With 10% extra	38 × 1.10	41.8 ft
8 ft pieces	41.8 ÷ 8 = 5.225	6
12 ft pieces	41.8 ÷ 12 = 3.483	4
14 ft pieces	41.8 ÷ 14 = 2.986	3
16 ft pieces	41.8 ÷ 16 = 2.613	3

Those are the minimums. Counted wall by wall, with the openings not subtracted, the same room needs 8 pieces of 8 foot, 6 of 12 foot and 4 each of 14 and 16 foot.

Baseboard for common room sizes

Linear feet of wall and pieces for one room with no openings and no extra. Each cell shows the minimum, then the wall by wall count when it is different.

Room	Linear ft	8 ft	12 ft	14 ft	16 ft
10 × 10	40	5 to 8	4	3 to 4	3 to 4
12 × 12	48	6 to 8	4	4	3 to 4
12 × 15	54	7 to 8	5 to 6	4 to 6	4
15 × 20	70	9 to 10	6 to 8	5 to 8	5 to 6
20 × 20	80	10 to 12	7 to 8	6 to 8	5 to 8

Tips for measuring and ordering

Measure the wall, not the floor. Baseboard follows the walls, so measure along them. If you only know the area, the square footage calculator will not give the walls, because the length depends on the shape.
Add rooms one by one. A hallway or closet is its own rectangle. Use “Add another room”.
Subtract only where the trim stops. Doorways and archways count. Windows do not, because baseboard sits at the floor.
Think about corners. Each inside and outside corner needs a cut, and cuts make waste. Use the extra box for the allowance your installer suggests.
Shoe molding and quarter round. They run along the same walls, so the same length applies. Enter the same rooms and compare the pieces for their lengths.
Check the lengths on the shelf. The pieces in the table are lengths from one manufacturer. Your supplier may stock others.

Frequently asked questions

How do I calculate how much baseboard I need?

Add up the length of every wall that gets baseboard. For a rectangular room that is 2 × (length + width). Subtract the width of each doorway or opening where the baseboard stops, add any extra you want, then divide by the length of the pieces you will buy and round up.

How much baseboard do I need for a 12x12 room?

The four walls add up to 2 × (12 + 12) = 48 linear feet before any doorways. That is 6 pieces of 8 foot baseboard if every offcut is reused, 4 pieces of 12 foot or 3 pieces of 16 foot. Subtract the doorway width and add your own extra on top.

Do I subtract doors and windows?

Subtract doorways and any other opening where the baseboard stops. Windows do not matter because the baseboard runs below them. Enter the width of each opening and how many there are, and the calculator subtracts them.

Why does the calculator show two numbers of pieces?

The first number is the minimum, which assumes you reuse every offcut. The second assumes each wall starts with a new piece, so an offcut from one wall is not used on the next. Real jobs fall between the two. The second number does not subtract openings, so it is a high estimate.

How much extra baseboard should I buy?

It depends on the number of corners, the joints and the skill of the installer. Alexandria Moulding, whose lengths this calculator uses, says on its product pages to add 10% to your calculated total to account for waste. Type the percentage you choose in the extra box and the length and the pieces update.

How much baseboard do I need for a 1500 sq ft house?

The floor area alone does not give the answer, because the length of baseboard depends on how many walls there are. A single square room of 1,500 square feet would have 4 × √1,500 = 154.9 feet of wall, but a house has many rooms, closets and hallways, and every wall adds length. Measure each room and enter it as a room or a wall.

Is this a calculator for baseboard heaters?

No. This one is for baseboard trim, the molding along the bottom of a wall. Sizing a hydronic or electric baseboard heater depends on how much heat the room loses, which is a different calculation.