Baseboard Calculator: How Much Baseboard Do I Need?

How to measure a room for baseboard

1. Sketch the room. A rough floor plan with every wall, closet, and bump-out drawn in keeps you from missing short runs. Metrie recommends starting this way.
2. Measure each wall at floor level. Pull the tape tight into the corners and keep it straight along the wall. Round up to the next half foot.
3. For a simple rectangle, measure length and width. That is all the calculator needs: it doubles them to get the perimeter. For an irregular room, add up all the walls, then enter any length and width that add up to half that total (for 50 ft of wall, 15 and 10 works).
4. Count the doorways. Baseboard stops at the door casing, so each doorway comes off the total. The calculator subtracts about 3 ft per doorway. Measure wider openings and adjust.
5. Note what else interrupts the wall. Cabinets, vanities, tubs, and built-ins usually have their own toe kick or trim, so leave those lengths out. Metrie also suggests checking that a tall baseboard will clear outlets and wall vents, and that its depth will not block floor vents.
6. Choose the piece length. Check what your store or supplier stocks. Home centers sell 8 ft pieces (Lowe's, for example), and moulding makers such as Alexandria Moulding and House of Moulding also offer 16 ft lengths.

Baseboard pieces by room size

These numbers use the calculator's formula with 10 percent extra. Rooms up to 12 x 12 assume one doorway; larger rooms assume two.

Check the count with a quick cut list

The formula treats baseboard like one long ribbon. Real walls are separate runs, and a piece that is too short for a wall leaves an offcut that may or may not fit somewhere else. A two-minute cut list catches problems before you are at the saw.

Take the default room. The walls are 12, 12, 10, and 10 ft, and the doorway splits one 10 ft wall into two short runs of about 3.5 ft each.

• With 8 ft pieces: each 12 ft wall takes a full piece plus 4 ft, and the solid 10 ft wall takes a full piece plus 2 ft. The two 4 ft pieces come from one board, the 2 ft piece and one 3.5 ft piece share another, and the last 3.5 ft piece needs its own board. That is 6 pieces, matching the calculator, with a seam on three walls.
• With 16 ft pieces: each 12 ft wall and the 10 ft wall gets one piece with no seam, and the two 3.5 ft runs come from the offcuts. That is 3 pieces and no seams at all.

If your cut list needs more pieces than the calculator, trust the cut list. It usually happens in rooms with many short walls.

Joints, corners, and other details

Scarf joints on long walls

When one wall is longer than your pieces, you need a joint in the middle. Home Depot's guide recommends a scarf joint, where both ends are mitered at 45 degrees in opposite directions, glued, and overlapped. Home Depot notes it is much stronger than a butt joint and has you nail through the joint into a stud, so plan joints to land over one.

Inside and outside corners

Outside corners are mitered. For inside corners, coping is the method Home Depot describes: you cut the profile of one piece so it fits against the face of the other for a seamless look. Every corner is a spot where material ends up as offcuts, which is why corner-heavy rooms need more than 10 percent extra.

Let the material acclimate

Bring the boards into the room a few days before you install them, as Home Depot advises, so they adjust to the room before you cut.

Painting the trim

If you are painting the baseboard, Behr suggests multiplying its total length by 0.5 ft to estimate square footage. The default room's 41 ft works out to about 20.5 sq ft, a small job: Sherwin-Williams puts a quart at about 100 sq ft, enough for two coats with room to spare. For wall paint, use our paint calculator.

Common mistakes to avoid

• Forgetting closets. A reach-in closet can add 10 ft or more of short runs, often with extra corners.
• Not subtracting built-ins. Kitchen cabinets, vanities, and tubs do not get baseboard. Measure only the exposed wall.
• Assuming every doorway is 3 ft. Double doors, sliders, and cased openings are much wider. Measure them.
• Buying only short pieces for long walls. More pieces means more seams to fill, sand, and paint. Buy long pieces for the long walls if you can get them home.
• Skipping the extra. Coped corners, test cuts, and one bad miter use up length fast. The 10 percent is not optional.
• Rounding down on the pieces. A result of 5.6 pieces means 6. You cannot make up the difference with offcuts on a wall that needs a full run.