About this calculator
The mitre saw setting to close any corner, or to build a frame or planter with any number of sides.
How it’s calculated
For a corner: mitre = (180° − corner) ÷ 2. For a regular polygon with n sides: mitre = 180° ÷ n, so a square is 45°, a hexagon 30° and an octagon 22.5°.
Worked example
With these inputs:
- I know
- The corner angle
- Corner angle
- 135
the result is:
- Saw miter setting
- 22.5°
- Angle from the board edge
- 67.5°
- Pieces cut at
- 22.5° each end
Tips from the trade
- A small error on each joint adds up around a polygon. Cut test pieces first.
- For bay windows, measure the actual wall angle rather than trusting the drawings.
Results are estimates for planning and pricing. Check quantities against your drawings, the manufacturer’s data and local building codes before ordering.