Linear feet, then pieces
Trim is sold in 8, 12 and 16-foot sticks priced by the linear foot. The calculation: room perimeter minus door openings, × 1.1 for miter waste, ÷ piece length = pieces to buy. Corner miters eat several inches per corner, and the piece you measure wrong is always the last one.
Crown needs more than the math
Crown molding runs on a compound angle — the spring angle means the wall and ceiling cuts differ, and inside/outside corners flip the miter direction. Cut test pieces from offcuts before touching the good stock. Baseboard and casing are square-cut at the wall, far more forgiving.
Sources and standards
Where these figures come from
Every formula on this page is implemented from the published reference material below. Where a value depends on a regional code, the calculator lets you override it rather than assuming one jurisdiction.
- Brick Industry Association — brick counts per square foot and mortar coverage rates.
- Vinyl Siding Institute — installation standards and product performance certification.
Figures, formulas and reference tables last verified: 19 September 2026.