How the baseboard calculator works
Baseboard is sold in pieces of set lengths, usually 8, 12 or 16 ft. The calculator finds the length of wall that gets baseboard, adds extra for miters, coped corners and mistakes, and divides by the piece length.
Baseboard length = room perimeter (or your wall total) − door openings × opening width
Pieces = baseboard length × (1 + extra %) ÷ piece length, rounded up
Shoe molding = the same length, in 8 ft pieces
Casing = 3 pieces of 7 ft per door side or window
Nails = 2 at every stud, studs 16 in apart (1 for shoe molding)
Caulk = (baseboard + casing length) ÷ 55 ft per tube
Worked example
A 12 by 14 ft bedroom has a perimeter of 52 ft. Take off one 36 in door opening and 49 ft of wall gets baseboard. With 10% extra that is 53.9 ft, so you need 4 pieces of 16 ft baseboard. Casing both sides of the door and two windows takes 12 pieces of 7 ft casing. Nails come to 174, one box, and caulking 115 ft of top edges takes 3 tubes.
Choosing piece lengths
| Piece | Good for | Watch out for |
|---|---|---|
| 16 ft | Most bedroom and living room walls in one length, no seams | Hard to carry; most cars cannot take them |
| 12 ft | Smaller rooms and hallways | Walls longer than 12 ft need a scarf joint |
| 8 ft | Bathrooms, closets and easy transport | More joints, more cutting and a little more waste |
Where you must join two pieces on a long wall, cut both ends at opposing 45° angles (a scarf joint), glue them and nail them over a stud, away from the middle of the wall where it shows most.
Measuring a room
- Rectangular room: measure the length and width along the floor, wall to wall.
- Any other shape: choose Wall by wall, measure each wall that gets baseboard and add them up. Include closet walls if you are trimming them.
- Count the door openings and open doorways. Measure one: the baseboard stops at the casing, so measure between the outer edges of the casing, about 36 in for a standard interior door.
- Skip walls behind built-in cabinets, tubs and vanities.
Before you buy
- Buy primed MDF or finger-jointed pine for painted trim; buy solid wood for stained trim and pick straight pieces.
- Let trim sit in the room for a day or two so it adjusts to the room's humidity before you cut it.
- Cope inside corners rather than mitering them. A coped joint is less likely to open up as the wood moves.
- Run a thin bead of paintable caulk along the top edge and in visible joints, then smooth it before painting.
Sources
The 10% allowance, scarf joints, coping and caulking follow This Old House's installation guide. Caulk coverage is DAP's figure of 55 linear feet per 10.1 oz tube at a 3/16 in bead.
Common questions
How do I calculate how much baseboard I need?
Add up the length of every wall, take off the width of each door opening, then add about 10% for cuts. A 12 by 14 foot room with one 36 inch door needs 49 feet, or about 54 feet with extra. That is 4 pieces of 16 ft baseboard.
How much extra baseboard should I buy?
About 10% for a simple room. Add more, around 15%, for rooms with many short walls and corners, or if you are learning to cope inside corners.
Should I buy 8, 12 or 16 foot baseboard?
Buy pieces at least as long as your longest wall when you can carry them, so the wall has no seam. 16 ft pieces cover most bedroom walls in one length. Shorter pieces are easier to transport but need more scarf joints.
Do I subtract doorways from baseboard?
Yes. Baseboard stops at the door casing, so take off the width of each opening, usually about 36 inches for an interior door. Open doorways without doors are subtracted the same way.
How many nails do I need for baseboard?
Plan on two finish nails at every stud, one into the stud and one lower into the bottom plate. Studs are usually 16 inches apart, so 100 feet of baseboard takes about 150 nails.