Cutting & joints
Coving / crown compound angles
- where
- mitre angle (°)
- spring angle to wall (°)
- included corner angle (°)
- bevel angle (°)
Explain this equation
Gives the mitre and bevel settings for cutting coving or crown moulding lying flat on a compound mitre saw.
φ is the spring angle, the angle between the back of the moulding and the wall once fitted. θ is the included corner angle between the walls. α is the mitre (table) setting and β the bevel (blade tilt) setting, both in degrees.
The moulding leans out from the wall, so the joint line is a compound angle in three dimensions. Laying it flat, the trigonometry splits that angle into a turn of the table and a tilt of the blade. The sin, cos and tan terms come from projecting the sprung moulding onto the saw bed.
For a common 38° spring at a 90° corner you get about 31.6° mitre and 33.9° bevel. A 45° spring gives 35.3° and 30°.
Watch out: these are magnitudes only. Left or right, and inside or outside corner, depend on your saw and how the moulding is placed. Always test-cut.
Calculate magnitude of compound settings for crown cut flat.
Enter your values to see the result.
Good to know
Spring is the installed angle between the back of the moulding and the wall, not ceiling. Angles are magnitudes only. Left/right, inside/outside and fence orientation follow the saw/moulding instructions. Test cuts are essential; this is not a universal profile cut list.
Limits
Crown angles are magnitudes for material cut flat, with spring measured to the wall.
Sources
This is a calculation aid, not a structural design or compliance certificate. Every default is an example, not a specification for your project.