Trim and Molding Calculator

Find the linear feet and number of pieces of baseboard, crown or casing for a room, with waste and cost.

Trim Type
Baseboard skips each door opening.
Opening plus casing, for baseboard.
Stock Length
For miters and coping; more for crown.
$
Fractions and decimals both work.
Linear Feet
Before waste
With waste
Pieces
Left over
Cost

Trim List

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RoomTypeLinear Ft.PiecesCostRemove

How to Figure Trim and Molding

Baseboard and crown run around the room, so start with the perimeter: two times length plus width. Baseboard stops at doors, so subtract each door's width. Crown runs all the way around. Door and window casing goes around each opening: for a door, both sides and the head; for a window, all four sides.

Baseboard = 2 × (length + width) − doors × door width
Door casing ≈ 2 × 7′ legs + head, per side   Window casing = window perimeter + miter allowance

For casing, the calculator figures 3½″-wide casing: each door head is the door width plus 7″, doors are cased on both sides, and each window adds eight casing widths for the mitered corners.

Add 10% to 15% for miters and scraps, and divide by the stock length to see how many pieces to buy. Buying longer pieces means fewer joints on long walls.

Worked Example

Tips

Measure each wall and buy pieces long enough to run it without a seam when you can; where a joint is needed, use a scarf joint over a stud. Cope inside corners on baseboard and crown for tighter joints. Crown is harder to cut and wastes more, so allow 15% or more. Paint or stain trim before installing to save time.