Crown Molding Calculator

Two numbers decide whether a crown job looks custom or looks fought: how much to buy, and the angle at every corner. Enter the room and this tool returns the linear feet, the stock pieces to order and the cost — then the exact compound miter and bevel to cut each corner flat on the saw, for standard 52/38 crown, 45/45 or any spring angle.
‍

‍

How the Corner Angles Are Solved

Crown sits on a spring angle — it leans out from the wall rather than lying flat against it — which is why a corner needs a compound cut, not a simple miter. Cut lying flat on the saw table, the two settings come from the spring angle S and the corner angle C:

miter = arctan( sin S ÷ tan(C ÷ 2) )
bevel = arcsin( cos S × cos(C ÷ 2) )

For a square 90° corner in standard 52/38 crown that resolves to a 31.6° miter and a 33.9° bevel; in 45/45 crown, 35.3° and 30°. The other way to cut crown is nested — held upside-down against the fence at its spring angle — where the corner reduces to a plain 45° miter with the blade vertical. Both are shown below; use whichever your saw and comfort favor, but never mix methods on one run.

‍

Corner Cut Reference

Inside and outside corners of the same angle share the same saw settings — what changes is which offcut you keep and which way you swing the miter. Always cut a scrap pair first and check the joint against a framing square before committing a full-length stick.

‍

Frequently Asked Questions

‍How do you calculate how much crown molding you need?
Perimeter = 2 × (length + width) for a rectangular room, plus 10–15% for miters and error, divided by your stock length and rounded up. Crown runs over doors and windows, so nothing is subtracted for openings.

‍What angle do you cut crown for a 90° corner?
Nested against the fence: a plain 45° miter. Cut flat: a compound 31.6° miter and 33.9° bevel for 52/38 crown, or 35.3° and 30° for 45/45.

‍What is the spring angle?
How far the crown tips off the wall. Standard crown is 52/38 (52° to the wall, 38° to the ceiling); the other common profile is 45/45. It sets both compound angles, so identify it first.

‍How much extra should I buy?
10–15% over the measured perimeter — crown wastes more than baseboard because every corner is a miter and coped joints lose a few inches per cut.

‍Inside vs outside corners?
Most rooms are all inside corners (often coped for a tight fit); outside corners wrap projections and are mitered. Same-angle corners use the same saw settings — only the waste side changes.