Crown Molding Angle Calculator

Crown molding is one of the most challenging trim carpentry tasks — and the biggest reason is the angles. Crown molding sits at an angle against both the wall and the ceiling simultaneously, which means you can’t just use a simple 45° miter to cut corners. You need a combination of miter angle and bevel angle that depends on both the wall corner angle and the molding’s spring angle.

Key terms:

Spring angle: The angle at which the crown sits against the wall. Most common values:

• 38° spring, very common, used by most standard crown molding profiles
• 45° spring, common in Europe and some US profiles
• 52° spring, less common, steeper profile

Miter angle: The rotation of the saw blade left or right from perpendicular.

Bevel angle: The tilt of the saw blade from vertical.

Wall corner angle: Interior corners of a room are ideally 90°, but can be slightly more or less due to construction variance. Exterior corners are typically 270° (or equivalently, 90° out).

For a standard 90° inside corner with 38° spring:

• Miter angle: 31.6° (set on the miter saw)
• Bevel angle: 33.9° (tilt of the blade)

For a standard 90° inside corner with 45° spring:

• Miter angle: 35.3°
• Bevel angle: 30°

The formulas: For a corner angle C (90° for a square room) and spring angle S:

Miter = arctan(cos(S) × tan(C/2)) Bevel = arcsin(sin(S) × sin(C/2))

Important note: These are the “flat” cutting angles. Many carpenters use the alternative “vertical” method where molding is held upside-down in the miter saw at its spring angle — in that case the miter angle changes but there is no bevel.

Practical tip: Always cut a test piece in scrap wood first. Label each cut piece with which end and which corner it belongs to before carrying it to the room.