Baseboard & Crown Molding Calculator

How to use the baseboard and crown molding calculator

1. Pick baseboard, crown or both.
2. Type the room’s length and width (12′ or 3.66 m both work) and the doors and openings: baseboard stops at each one.
3. Open Room shape, lengths sold, doors and corners to type every wall in order round the room (an L-shaped room, a bump-out), to turn off the stick lengths your store does not sell, and to set the door width, the corner angle (135° for a bay window) and your crown’s profile.
4. You get the sticks to buy, the cut list stick by stick, every stick drawn to scale, the corner cuts and the saw settings. Copy link keeps the result.

Baseboard and crown molding for common room sizes

Baseboard: the room less one 36″ door. Crown: the whole room, plus one 8 ft stick for test cuts. The mix is the one that buys the least length with no joint on a wall shorter than 16 ft. “The 10% rule” is the usual shortcut — the feet ÷ 8 × 1.1, in 8 ft sticks — which ignores where the cuts fall.

Crown molding angles: the miter and bevel for every corner

Crown laid flat on the saw, its back on the table. The 90° row is the crown table printed in Makita’s LS1219 miter saw manual; every row matches Joe Fusco’s crown angle chart, which runs from 1° to 179°.

The rules behind the cut list

The stick lengths

Lowe’s puts it plainly: prefinished, MDF and décor molding usually come in 8 ft lengths, and standard unfinished wood molding in 8, 10 and 12 ft. Metrie also sells primed MDF baseboard 16 ft long. Lowe’s advice is to work out which lengths cover the walls “with the least waste” — its example is a 6 ft and a 5 ft wall cut from one 12 ft piece — and that is what the calculator does: it tries every mix of the lengths you leave on and buys the least length, then the fewest sticks.

One piece a wall, and where the joints go

Every wall gets one piece when a stick is long enough. A longer wall is spliced with a scarf joint (both ends cut at 45° so they overlap), in as few pieces as it takes, and the calculator tries every way of cutting it, with no spliced piece shorter than 2 ft so each one reaches a stud. Pieces share a stick only with 1″ each to spare for the saw and a test fit; Home Depot cuts a coped piece ⅛″ long so it pushes the joint closed. That is why two 4 ft pieces never come out of one 8 ft stick.

Doors, corners and the saw

Baseboard stops at each door’s casing, so each door takes its width, 36″ by default, off a wall. Crown runs over the doors. In a room with square corners there are always four more inside corners than outside ones. The usual way to join an inside corner is to cope it: one piece cut square into the corner, the next one’s end cut to its profile, which hides a corner that is not quite square. Outside corners are mitered. Lowe’s also describes corner blocks, which need no corner cuts at all: one per corner, and a divider block in any wall over 8 ft. For crown laid flat, the saw settings come from the crown’s spring angle, which is 38° for 52/38 crown and 45° for 45/45, and from the corner itself. Home Depot and Makita both tell you to practise on scrap first, so the crown count includes one more stick.

Worked examples

An L-shaped room: walls of 14, 12, 4, 2, 10 and 10 ft, with two doors. Six walls make 5 inside corners and 1 outside. It takes 1 × 16 ft + 1 × 12 ft + 2 × 10 ft of baseboard: the 4 ft and 2 ft walls come out of the offcuts of the two long walls, with no joints.

Crown in a 20 × 14 ft room, where the store sells only 8 and 12 ft. The 20 ft walls outrun a 12 ft stick, so each is spliced twice: 6 × 12 ft + 1 × 8 ft (the 8 ft for test cuts), with 4 scarf joints. A 16 ft length, where it is sold, gets the 14 ft walls in one piece each.

Crown round a bay window’s 135° corners. 52/38 crown laid flat: a 14.3° miter and a 17.6° bevel. Baseboard there takes a 22.5° miter on each piece.

Common baseboard and crown mistakes

• Buying by the 10% rule for 12 ft walls in 8 ft sticks. In a 12 × 12 room the rule says 7 sticks of crown. Each wall takes a whole stick and a 4 ft piece, and two 4 ft pieces never come out of one 8 ft stick, so the cuts need 8, and one more to practise on.
• A splice in the middle of a short wall. If a wall is shorter than a stick you can buy, buy the longer stick: a joint is the hardest thing to hide.
• Mitering inside corners on walls that are not square. The miter opens up; a coped corner stays closed.
• Setting a 45° bevel for crown. Crown laid flat takes both a miter and a bevel: 31.6° and 33.9° for 52/38 crown at a square corner.
• No test piece. Walls and ceilings are rarely true. Cut a test joint from scrap before the first real piece.

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