Find the miter saw angle for a corner or an equal-sided frame. Enter a corner angle, or the number of sides for a frame or ring.
Usage Tip
Measure the actual corner with an angle finder rather than assuming 90°. Cut scrap at the calculated angle, hold it in the corner, and fine-tune before cutting your real molding.
For an N-sided frame: angle = 180° ÷ N
Interior angle of an N-gon = (N − 2) × 180° ÷ N
For equal-sided frames and rings, every cut is 180° ÷ N.
Walls and corners are rarely exactly 90°; measure the real angle with a protractor or angle finder and cut test pieces first.
For crown molding the saw also needs a bevel (a compound miter) — this gives the flat miter only.
What Is a Miter Cut?
A miter cut is an angled cut across the face of a board so two pieces meet to form a corner. Cut both ends to the right angle and the joint closes tight with no gap. The trick is that the number you set on the saw is not the same as the corner angle – and that single confusion is behind most trim that does not fit.
Saw Setting vs Miter Angle (the part everyone gets wrong)
There are two different numbers floating around, and charts disagree because they quietly use different ones:
- Saw setting = the angle you dial into the miter saw, measured from a square (0°) crosscut. For a corner angle C, it is 90 − C/2. A 90° corner = 45°, a 120° corner = 30°, a 135° corner = 22.5°.
- Miter angle (half the corner) = C/2. A 90° corner = 45°, a 120° corner = 60°, a 135° corner = 67.5°. This is the angle of the cut line across the board, not the saw dial.
Miter Angle Chart
Common corners, showing both numbers so there is no guessing:
| Corner angle | Miter angle (half) | Saw setting (dial this) |
|---|---|---|
| 60° | 30° | 60° |
| 90° | 45° | 45° |
| 108° | 54° | 36° |
| 120° | 60° | 30° |
| 135° | 67.5° | 22.5° |
| 150° | 75° | 15° |
Crown Molding Guide
Crown sits at an angle to the wall (the spring angle, usually 38° or 45°), so cutting it is a compound problem: you set both a miter and a bevel. The easiest shop method is to lay the crown flat on the saw and use compound settings. For a 90° corner:
| Spring angle | Miter (flat) | Bevel (flat) |
|---|---|---|
| 38° | 31.6° | 33.9° |
| 45° | 35.3° | 30.0° |
| 52° | 38.3° | 25.8° |
If you cut crown nested (held against the fence at its spring angle), you set a simple miter instead and no bevel – but the molding must be held at the exact spring angle every time. Most people find the flat method more repeatable. The calculator computes both miter and bevel for any corner and spring angle.
Baseboard & Trim Guide
Baseboard miters are simple miters: a 90° inside or outside corner is 45° on the saw. Inside corners are often coped instead – one piece butts square, the second is cut at 45° and the profile traced and cut back so it laps over the first. Coping hides gaps when corners are not truly square, which they rarely are.
Compound Miter Guide
A compound miter combines a miter (blade swung left/right) with a bevel (blade tilted). You need it for crown, sloped boxes, hoppers, and anything where the faces are not vertical. For a joint with corner angle C and a face slope/spring angle S, the flat-cut settings are miter = atan(sin S × tan(90−C/2)) and bevel = asin(cos S × sin(90−C/2)). The calculator does the trig – pick Compound or Crown mode and read off both.
Picture Frame & Polygon Guide
A regular many-sided frame splits evenly: each joint saw setting is 180° ÷ number of sides. A 4-side picture frame is 45°, a hexagon is 30°, an octagon is 22.5°.
| Sides | Shape | Interior angle | Saw setting |
|---|---|---|---|
| 3 | Triangle | 60° | 60° |
| 4 | Square frame | 90° | 45° |
| 5 | Pentagon | 108° | 36° |
| 6 | Hexagon | 120° | 30° |
| 8 | Octagon | 135° | 22.5° |
| 12 | Dodecagon | 150° | 15° |
Inside vs Outside Corners
The angle is the same; the orientation flips. On an inside corner the long point of the cut is at the back (against the wall). On an outside corner the long point is at the front (the exposed edge). Mark your long point before cutting and you will not reverse a piece. For a pair of pieces, swing the saw one way for the left piece and the mirror way for the right.
Saw Setup & Calibration
- Check that 0° is a true square cut – cut a scrap, flip it, and butt the two cuts; any gap is double your error.
- Verify 45° with a known-square framing square or a test frame.
- Single-bevel saws cut one bevel direction – flip the molding for the mirrored piece. Dual-bevel saws tilt both ways, so no flip.
- Cut test pieces in scrap before your good stock.
- Account for blade kerf when a cut must land on a mark.
Common Trim Mistakes
- Dialing the half-corner angle instead of the saw setting.
- Assuming every corner is exactly 90° – most are a degree or two off.
- Mixing up inside vs outside long-point direction.
- Forgetting the bevel on crown and cutting a flat miter only.
- Not measuring the actual corner with a protractor or bevel gauge first.
Frequently Asked Questions
What miter angle do I set for a 90 degree corner?
45° on the saw – each of the two pieces is cut at 45° so they add up to 90°.
Why does my miter chart say 60 for a 120 degree corner but the calculator says 30?
60° is half the corner (the miter angle); 30° is the saw setting you actually dial (90 − 120/2). Set 30° on the saw for a 120° corner.
What are the crown molding angles for a 90 degree corner?
Cut flat, a 38° spring crown is about 31.6° miter and 33.9° bevel; a 45° spring crown is about 35.3° miter and 30° bevel.
What is a compound miter?
A cut that uses both a miter (blade swung) and a bevel (blade tilted) at the same time, needed for crown and any non-vertical faces.
What if my corner is not exactly 90 degrees?
Measure the real angle with a protractor or bevel gauge and enter it. Each piece gets half the difference, so a 92° corner is a 44° saw setting, not 45°.
What is the miter angle for a picture frame?
A standard four-sided frame is 45° per corner. For other shapes, divide 180 by the number of sides.
Related Carpentry Calculators
Note: real-world corners are rarely perfect – always measure the actual angle in the field with a protractor or bevel gauge before cutting. Crown results depend on the molding spring angle, and saw scales drift, so calibrate your saw and cut test pieces in scrap first. Angles are in degrees in both metric and imperial work. General woodworking guidance, not a substitute for measuring your own material.