Get the right miter saw setting every time. Enter the number of sides of a frame or box, or the angle of a corner, to get the miter angle; for crown molding enter the spring angle and wall corner to get the compound miter and bevel, plus the nested setting.
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What are you cutting?
4 for a picture frame, 6 hexagon, 8 octagon
°
90 for a square corner, 135 for a bay window wall
°
Any unit, long point to long point
Same unit as the side length
Enter your values to see the result.
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How to use the Miter Angle Calculator
Choose what you are cutting: a polygon frame, a single corner, or crown molding.
Enter the number of sides or the corner angle (measure walls with an angle finder; they are often not exactly 90°).
For crown, pick the spring angle printed on the molding or measured against a square.
Set the saw to the miter (and bevel) shown and make test cuts on scrap first.
Miter angle formulas
Polygon or frame: miter = 180° ÷ number of sides
Single corner: miter = 90° − corner angle ÷ 2 (saw scale measured from a square cut)
Crown, flat (compound): miter = atan(sin S ÷ tan(W ÷ 2)), bevel = asin(cos S × cos(W ÷ 2))
Crown, nested: miter = 90° − W ÷ 2, bevel = 0°
S is the crown spring angle and W the wall corner angle. Most miter saws read 0° for a square cut, which is the convention used here. If your tool reads 90° for a square cut, use the "angle of cut to the board edge" value instead.
Crown molding settings for a 90° corner
Crown type
Spring angle
Flat miter
Flat bevel
Nested miter
52/38
38°
31.62°
33.86°
45°
45/45
45°
35.26°
30.00°
45°
Steep (52° spring)
52°
38.24°
25.81°
45°
Polygon quick reference
Shape
Sides
Miter setting
Triangle
3
60°
Square / frame
4
45°
Pentagon
5
36°
Hexagon
6
30°
Octagon
8
22.5°
Dodecagon
12
15°
Frequently asked questions
How do I calculate a miter angle for a polygon?
Divide 180° by the number of sides. A 4-sided frame needs 45° cuts, a hexagon 30°, an octagon 22.5° and a 12-sided shape 15°. Each piece gets that cut at both ends, and the pieces together close a full 360°.
What miter angle do I need for a corner that is not 90 degrees?
Set the saw to 90° minus half the corner angle. A 135° bay window corner needs 22.5° cuts and a 120° corner needs 30°. Measure the real corner with an angle finder, because walls are often off by a degree or two.
What are the miter and bevel settings for crown molding?
With crown laid flat, the miter is atan(sin S ÷ tan(W/2)) and the bevel is asin(cos S × cos(W/2)), where S is the spring angle and W the wall corner. For common 52/38 crown on a 90° corner that gives a 31.62° miter and 33.86° bevel; 45/45 crown needs 35.26° and 30°.
What is the crown molding spring angle?
It is the angle at which the molding sits between the wall and ceiling. Most US crown is 52/38 (about 38° spring) or 45/45. Hold the molding in a framing square as it would sit on the wall and ceiling to measure it if it is not printed on the label.
What does nested mean for crown molding?
Nested means cutting the crown upside down and backwards on the saw, with its flats resting against the fence and table exactly as they sit against the wall and ceiling. Then you only need a miter (45° for a square corner) and no bevel.
Why don't my miters close?
Usually the corner is not the angle you assumed, or the saw's 0° is slightly off. Measure the corner, split the difference, check the saw with a square and make test cuts on scrap before cutting your stock.
Is my data sent anywhere?
No. All calculations run in your browser.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.