How to Calculate Angle Cuts (Miter Angle Chart)
Part of Interior & Finishes
Quick answer
To make two boards meet at a corner, cut each one at half the corner angle. A square 90° corner needs two 45° miters; a 120° corner needs two 60° miters. The rule is: miter angle = corner angle ÷ 2. For odd-shaped rooms, measure the actual corner angle first — walls are rarely a perfect 90°.
Most trim, framing and woodworking joints are miters: two pieces each cut at an angle so they meet cleanly. The single rule behind almost every cut is that the two pieces split the corner evenly.
The rule
Miter angle (each piece) = Corner angle ÷ 2
Note that a miter saw reads angles from 0° (a straight, square cut), so the saw setting is usually 90° − miter angle. For a 45° miter the saw is set to 45°; the two numbers happen to match only at a square corner.
Miter chart for common corners
| Corner angle | Miter per piece | Miter saw setting |
|---|---|---|
| 90° (square) | 45° | 45° |
| 120° (hexagon) | 60° | 30° |
| 135° (octagon) | 67.5° | 22.5° |
| 108° (pentagon) | 54° | 36° |
| 60° | 30° | 60° |
Tips for real-world corners
- Measure the actual corner with an angle finder or protractor — drywall corners are often 88–92°, not exactly 90°.
- Split whatever you measure in half for each piece's miter.
- Cut a test scrap and check the fit before cutting your finish stock.
- For crown molding, the wall angle and the spring angle interact — use a crown chart or a saw with crown settings.
Once your angles are set, the board-foot and linear-feet calculators help you total the material and order the right amount of trim with a waste allowance for the cuts.
FAQs
What angle do I cut for a 90 degree corner?
Each piece is cut at 45° (90 ÷ 2). On a standard miter saw that's the 45° setting. Two 45° cuts meet to form the square corner.
How do I cut a corner that isn't 90 degrees?
Measure the actual corner angle, then cut each piece at half that angle. A 120° corner needs two 60° miters; a 100° corner needs two 50° miters. An angle finder makes measuring odd corners quick.
What's the difference between a miter and a bevel?
A miter is an angled cut across the face/width of the board (turning a corner in plan), while a bevel is angled through the thickness. A compound cut combines both — common in crown molding and complex trim.