Baseboard & Trim Calculator

How the trim count works

The measurement is simple: perimeter − door openings. A 12 by 14 foot room is 52 feet around, and two 3 foot doorways take 6 feet out of that, so 46 linear feet of baseboard actually touches the wall. The interesting part is everything that happens between that number and what you carry out of the store.

Why 15 percent, when flooring gets 10

Flooring waste is edge cuts, and an edge cut usually leaves a usable strip. Trim waste is corners, and a corner cut leaves nothing.

An inside corner is coped: one piece butts into the corner square, and the other gets its profile scribed to match, which means cutting a 45, following the profile line with a coping saw, and back-cutting the whole thing. Get the angle wrong, and the piece is short by the width of the base. An outside corner is a pair of 45 degree miters, and because no wall corner is exactly 90 degrees, the first pair is usually a test cut. Both ends of every piece are opportunities to be an inch short.

15 percent covers a normal room. Push it to 20 on a room with several outside corners, a bay, or a tall profile where a bad cut wastes more stock. Pull it back toward 10 only if you are running plain square-edge stock with butt joints.

Why longer stock is worth the hassle

A joint in the middle of a wall is called a scarf joint, and it is the one part of a trim job that is hard to hide. Two 45 degree cuts overlap so the seam does not open when the wood moves, and it still needs glue, nails on both sides, filler, and sanding, and it will still catch the light.

So the stock length that matters is not the one that minimizes waste on paper. It is the shortest one that covers your longest wall in a single piece. A 14 foot wall run out of 16 foot stock has one offcut and no joints. The same wall out of 8 foot stock has a scarf joint in the middle of the room's most visible surface, and the offcuts are too short to use anywhere but a closet.

Measure the longest single run before you pick a stock length, then buy the next size up.

Doors, and what else comes off

Only cased openings come off the perimeter, because the casing takes the place of the base. Take off the full width of the opening including the casing, not just the door slab. What does not come off: a fireplace, a built-in, or a cabinet run, unless the base genuinely stops there, and even then it usually returns into the obstruction and needs a short piece with a finished end.

Ordering with the flooring

Base goes on after the floor, so if both are on the list, order them together and let the floor go down first. Run the same room through the flooring calculator for boxes, and note that shoe moulding or quarter round, if you are using it, is a second run of the same linear footage. Count it separately.