How much baseboard do I need?

Corners are where the material goes

The linear footage is simple: the room perimeter, minus the width of every doorway. A 12 by 15 foot room has a 54 foot perimeter, and two 3 foot doorways bring it down to 48 feet of trim.

Turning that into pieces is where judgement comes in. Baseboard is sold in fixed lengths — commonly 8, 12 or 16 feet — and the count here is the total divided by the length you can buy. But trim is not like flooring: you cannot butt two short pieces together in the middle of a wall and expect it to look right. Wherever possible each wall wants a single piece, which means a 14 foot wall needs a 16 foot stick and the offcut is only useful if another wall happens to be under 2 feet.

That is what the waste allowance is really covering. Every inside corner is a coped or mitred joint, every outside corner is a mitre, and a mitre cut a degree off wastes the end of the piece. Ten percent is fine for a plain rectangular room; go to 15% once the room has more than four corners, or if you are coping the inside joints by hand.

One practical note on buying: check the pieces for bow before you load them. Baseboard is thin and long, and a stick with a curve in it will fight you the whole way along a wall. Sight down each one on the rack.

A worked example: four rooms at once

Trim is usually bought for several rooms at a time. Take two bedrooms (12 × 14 and 11 × 12, one door each), a 14 × 18 living room with two openings and a 5 × 8 bathroom. The perimeters are 52, 46, 64 and 26 feet; subtracting 3 feet for each of the five doorways leaves 173 linear feet. With 10% waste that is 190 feet, or 12 pieces of 16 feet.

Before you buy, sort the walls by length. Each wall wants a single piece where possible, so a 14-foot wall takes a 16-foot stick, a 12-foot wall a 12, and the short walls come out of the offcuts. A quick list of wall lengths turns into a much more accurate order than the total alone.

Which length to buy

The other trim in the room

• Shoe molding or quarter round: about the same linear footage as the baseboard, if you are using it to cover the gap at the floor (it is standard over laminate and vinyl plank).
• Door casing: roughly 17 feet per side of a standard interior door (two legs of about 7 feet plus a head).
• Nails, caulk and filler: nail at every stud, about every 16 inches, and caulk the top edge where it meets the wall.

Mistakes that show

• Mitering inside corners. Mitered inside corners open up as the wall moves with the seasons. A coped joint, where one piece is cut to the profile of the other, stays tight.
• Joining pieces with a square cut. Where a joint is unavoidable on a long wall, use a scarf joint (two 45° cuts overlapping) over a stud.
• Installing before the floor. If new flooring is going down, install it first, then the baseboard, so the trim covers the expansion gap.

What it costs

Primed MDF baseboard commonly costs about $1 to $2.50 per linear foot in the US, finger-jointed pine about $1.50 to $3, and hardwood more. For the 190 feet in the example, that is roughly $191 to $476 in MDF. Prices vary by profile and height.