How to use the miter angle calculator
- Measure the included angle between the two pieces at the joint.
- Enter that included angle, between 0 and 180 degrees.
- Read the saw setting, where zero represents a square crosscut. Mirror the cuts to form the joint.
The formula
Equal miter saw setting = (180° − included corner angle) ÷ 2
Worked example
For a 90° included corner, set each miter to 45°. A 120° included corner takes 30° on each piece.
Before you measure and cut
Angle finders may report either the included angle or its supplement. Verify which reading your tool displays.
This is a flat, equal-miter joint. Crown molding laid flat requires both miter and bevel, calculated separately.
Frequently asked questions
Why isn’t the saw setting always half the corner angle?
The saw scale is referenced to a square crosscut. The setting is half of the supplement of the included angle. At 90°, the two conventions happen to match.
Can I use this for unequal widths?
It computes equal angles. A visually balanced joint between different widths may require unequal miters.