How to use compound crown molding miter
What this calculation does
A crown-moulding compound cut resolves an entered wall corner and spring angle into paired saw miter and bevel settings.
Measure the inside wall angle and use the spring-angle convention specified by the moulding and saw instructions.
Enter the measurements
- Inside wall corner angle: Enter the inside angle between the two walls.
- Crown spring angle from wall: Enter crown spring angle measured from the wall.
Formula and variables
Miter = atan(sin(spring angle) ÷ tan(wall angle ÷ 2)). Bevel = asin(cos(spring angle) × cos(wall angle ÷ 2)). Trigonometric outputs are converted to degrees.
The trigonometric equations produce settings in degrees. Saw orientation and the meaning of its scale must match the stated convention.
Read the result
For a 90 degree wall and 38 degree spring angle, the settings are about 31.619 degrees miter and 33.863 degrees bevel.
Worked example
Inputs: 90° inside wall corner and 38° spring angle
- Half wall angle = 90÷2 = 45°; apply the stated sine/tangent equation for miter.
- The equations give miter ≈31.619° and bevel ≈33.863°.
Expected result: about 31.619° miter and 33.863° bevel
Frequently asked questions
Does this tell me which way to tilt the saw?
No. Cut orientation and moulding position depend on the saw and setup; confirm with a test cut.
Will it correct an out-of-square wall?
No. Enter the measured corner and verify fit in place.
Conditions, presets and technical notes
Use the named spring-angle convention measured from the wall and the miter/bevel convention described by the selected saw manual. This does not set cut orientation, molding position, saw calibration or account for non-planar walls; confirm with a test cut.