Practical tools for measured work
Compound Crown Molding Miter & Bevel Calculator
Calculate the flat-cut compound miter and bevel saw settings for crown molding from spring angle and wall corner angle.
Angle between the molding's back and the wall when installed - commonly 38° or 45°, check your molding's profile spec.
90° = a standard square inside/outside corner. Enter the actual angle for an out-of-square wall or a bay-window corner.
Run the molding flat on the saw table, upside-down and backwards (top of the molding against the fence) - that's what these compound miter and bevel settings assume.
How it works
How to use it: enter your crown molding's spring angle (the angle its back makes with the wall - check the profile spec, or a rafter/protractor against an installed sample; 38° and 45° are the two most common) and the wall corner's plan angle (90° for a standard square corner). This gives the compound miter and bevel settings for cutting the molding flat on the saw table, which is how most trim carpenters cut crown - no crown stop or angled fence needed.
Calculation. With spring angle S and corner angle A:
Miter = atan(sin(S) × tan(A/2)), Bevel = asin(cos(S) × sin(A/2))
Worked checks. 38° spring at a 90° corner gives 31.62° miter / 33.86° bevel; 45° spring at a 90° corner gives the classic 35.26° miter / 30° bevel; 52° spring at a 90° corner gives 38.24° miter / 25.81° - all matching commonly published crown-molding cut-angle references.
Current-input example
The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.
- Spring angle
- 38 deg
- Wall corner angle
- 90 deg
Primary result: Miter angle (saw table): 31.62 deg.
Before using the result
- Measure from the datum or reference edge described by this tool, and do not mix inside, outside and centerline dimensions.
- Keep inputs in the displayed units and preserve more precision than the final cutting or purchasing tolerance requires.
- When the result is close to a limit, verify it with a test piece, field measurement, manufacturer drawing or qualified project professional.
Limitations
This covers vertical walls meeting at any plan angle - including out-of-square corners and bay-window returns. It does not solve a true sloped/vaulted ceiling transition, where crown runs from a normal wall-ceiling corner up onto a raked ceiling: that is a genuinely different, asymmetric 3D problem (the two sides of the joint aren't mirror images), and this formula does not apply to it. Always cut a test piece from scrap before committing molding.
Frequently asked questions
What if I don't know my molding's spring angle?
Check the manufacturer's profile spec sheet, or hold a full protractor against the back of a sample piece against a flat surface - 38° and 45° cover the large majority of stock crown profiles, with 45° being common for simpler, symmetric profiles.
Why cut crown flat instead of standing it up against an angled fence?
The flat method only needs the miter saw's two normal adjustments (table rotation and blade tilt), with no crown stop or jig required - at the cost of needing both numbers set precisely, which is exactly what this calculator gives you.
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