Calculator
Mitre angle calculator
Enter the number of sides of a frame or box, or the measured angle of a wall corner in degrees. You get the setting for the saw's mitre scale for each piece.
In short
For a closed frame with N equal sides, each piece is cut at 180 ÷ N degrees off square (4 sides = 45°, 6 sides = 30°, 8 sides = 22.5°). For a wall corner of A degrees, cut each piece at (180 − A) ÷ 2 off square: a 90° corner needs 45°, a 135° corner 22.5°.
Work out the setting
Mitre scale setting, each piece
30°
180 ÷ 6 = 30.00°
- Saw scales read 0 at square, so the value shown is the number to set on the mitre scale. Rounded to 0.5 degree.
- Cut both ends of every piece at this setting, with opposite pieces the same length.
Common settings
| Job | Angle | Mitre setting |
|---|---|---|
| Triangle frame | 3 sides | 60° |
| Picture frame or box | 4 sides | 45° |
| Hexagon planter | 6 sides | 30° |
| Octagon | 8 sides | 22.5° |
| Square room corner | 90° | 45° |
| Bay window corner | 135° | 22.5° |
Check the corner with a sliding bevel or an angle finder rather than assuming 90 degrees. Older UK walls are often a degree or two out, and a test cut on an offcut saves a length of skirting.
Mitre
An angle across the face.
Bevel
A tilt through the thickness.
Compound
Both at once, as on coving.