Miter angle calculator
This miter angle calculator gives you the angle to set on your miter or chop saw: choose wall corner, polygon frame or sloped sides.
Example: What are you cutting: Trim at a wall corner · Corner angle 90 ° → Result: Miter angle on the saw: 45°. Source: Wikipedia – Gehrung (miter): miter angle = half the angle between the parts. Updated: .
How it is calculated
The miter angle is half the supplement of the corner angle: (180° − corner angle) / 2. For a right-angled corner that is 45°, for a hexagon 30°, for an octagon 22.5°.
How it is calculated
Two pieces meet at the corner and each gets half the angular deviation as its cut. For a regular n-gon the interior angle is 180°·(n−2)/n, so the miter is 180°/n. If the sides are sloped (hopper, planter box, frame), the miter plane bisects the angle between two side faces; its position in the board gives two settings: miter on the table and bevel on the blade.
Good to know
- Walls are rarely exactly square: measure the corner angle (with an angle finder) and enter it instead of assuming 90°.
- An error of 0.5° per cut adds up to visible gaps on frames. Always test on an offcut first.
- The result applies to the angles at the saw; material thickness and wall unevenness are not included.
Frequently asked questions
How do you calculate the miter angle?
Miter angle = (180° − corner angle) / 2. For a 90° room corner that is 45° for each of the two pieces.
What miter angle is used for a hexagon or octagon?
For a regular n-gon 180°/n: hexagon 30°, octagon 22.5°, pentagon 36°.
What if the corner is not 90°?
Measure the corner angle and enter it. At 92° you get 44° instead of 45°; otherwise a gap stays open.
What does bevel mean for sloped sides?
For hoppers or boxes with sloped sides the blade has to be tilted in addition to the miter. The calculator gives both values.
Sources and legal basis
- Wikipedia – Gehrung (miter): miter angle = half the angle between the parts
- Wikipedia – Miter joint: calculating miter and bevel angles
As of: · Editorial policy
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