Compound cuts combine a miter angle and a bevel angle at the same time. Crown molding is the classic example: the molding sits at a spring angle, while the wall corner creates a second angle. The calculator below gives the two saw settings for cutting crown molding flat on the saw table.
Compound Angle Formula
For crown molding cut flat, let S be the spring angle and C the included wall-corner angle. The calculator uses:
Miter = atan( sin(S) / tan(C/2) )
Bevel = asin( cos(S) × cos(C/2) )
A common 38° spring angle at a 90° wall corner gives approximately 31.62° miter and 33.86° bevel.
Quick Reference
| Spring angle | Corner | Miter | Bevel |
|---|---|---|---|
| 38° | 90° | 31.62° | 33.86° |
| 45° | 90° | 35.26° | 30.00° |
| 52° | 90° | 38.24° | 25.81° |
How to Use the Result
- Measure the actual wall corner rather than assuming it is exactly 90°.
- Confirm the molding spring angle from the profile or packaging.
- Enter both values in the calculator.
- Set the saw table to the miter result and tilt the blade to the bevel result.
- Cut scrap first and dry-fit before cutting finished stock.
Simple Miter vs Compound Miter
A simple miter joint lies in one plane, so only the saw table rotates. A compound cut changes direction in two planes, so both miter and bevel settings matter. Picture frames usually use a simple miter; crown molding cut flat requires a compound setup.
Common Mistakes
- Mixing up spring angle and corner angle.
- Using the flat-cut numbers while holding crown nested against the fence.
- Assuming walls are perfectly square.
- Reading a saw scale from a different reference convention.
- Skipping a test cut.
Frequently Asked Questions
What are the standard crown molding angles for a 90° corner?
For 38° spring crown cut flat, the commonly used settings are about 31.62° miter and 33.86° bevel.
Why do I need both a miter and a bevel?
Because the molding is oriented at a spring angle while also turning through the wall corner. The cut plane therefore has to rotate in two axes.
Can I use this for non-90° corners?
Yes. Enter the measured included wall angle. The calculator recomputes both settings.
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