Crown molding miter and bevel angles
Crown molding sits at an angle between wall and ceiling (its spring angle), so a flat cut needs both a miter and a bevel. The two settings come from trigonometry: miter = arctan(sin S ÷ tan(W/2)) and bevel = arcsin(cos S × cos(W/2)), where S is the spring angle and W the wall corner.
| Corner | 38° crown: miter | 38° crown: bevel | 45° crown: miter | 45° crown: bevel |
|---|---|---|---|---|
| 90° | 31.62° | 33.86° | 35.26° | 30° |
| 120° | 19.57° | 23.2° | 22.21° | 20.7° |
| 135° | 14.31° | 17.55° | 16.32° | 15.7° |
| 150° | 9.37° | 11.77° | 10.73° | 10.55° |
| 270° (outside) | 31.62° | 33.86° | 35.26° | 30° |
A 270° outside corner uses the same angles as 90°, with the pieces mirrored.
Cutting crown nested instead
Nested (upside down and backwards against the fence) cutting needs only a miter: (180° − corner) ÷ 2, so 45° for a square corner, with the bevel at zero. It is simpler on a small saw but requires a fence tall enough to hold the molding at its spring angle.
How much crown molding to buy
Crown follows the room perimeter. Add a larger waste allowance than for baseboard, 15% by default, because test cuts and coped joints use more. The baseboard calculator handles base and casing for the same room, and the feet and inches calculator adds up odd wall lengths.
Common crown molding mistakes
- Wrong spring angle. Check the profile: a 52/38 crown and a 45/45 crown need different settings.
- Corners assumed square. Measure the real corner with an angle finder; walls are often 88–92°.
- Cutting on the wrong side of the blade. Mark left and right pieces before cutting.
Frequently asked questions
What angle do you cut crown molding for a 90° corner?
Flat on the saw: 31.62° miter and 33.86° bevel for 38° crown; 35.26° and 30° for 45° crown. Nested: 45° miter, no bevel.
What is the spring angle of crown molding?
The angle between the back of the molding and the wall. Common profiles are 38° (sold as 52/38) and 45°.
How much crown molding do I need?
The room perimeter plus about 15% for test cuts and joints.