Miter angle calculator for frames and polygons
Pick the number of sides and get the miter saw setting, the angle from the edge, and the long-point and short-point length of each piece. Square frames, hexagons, octagons.
A picture frame is 45°, everyone knows that. A hexagon or an octagon is where I would get it wrong. This gives the saw setting and the piece lengths for any regular shape.
Everything is calculated in your browser. Nothing is saved or sent.
How it works
In a regular shape with n sides, each corner measures (n − 2) × 180 ÷ n degrees.1 Two pieces meet at each corner and split it, so each piece is cut at half the bend. Measured from square, which is how most miter saw scales read, that is 180 ÷ n degrees: 45° for 4 sides, 30° for 6, 22.5° for 8.
Some protractors and sliding bevels measure from the edge of the board instead. That is 90° minus the saw setting, so the page shows both.
Pieces are measured on the long point, the outside edge. The inside edge is shorter by 2 × width × tan(saw angle). For a square frame with 50 mm stock that is 100 mm shorter.
Common questions
What angle do I cut for a hexagon?
30° on a miter saw scale that reads 0° at square, which is 60° measured from the edge of the board.
Why do my miters leave a gap?
A small error repeats at every corner. On an octagon there are 16 cuts, so half a degree off on each adds up. Test on scrap first.
Where this comes from
- Wikipedia. Regular polygon. Encyclopedia. Wikipedia Consulted 1 Nov 2026.