Mitre Angle Calculator
Compound cuts move both angles at once.
Work out Mitre Angle. Compound cuts move both angles at once. Shows the working, not just the answer.
Mitre angle
30°
6 sides, flat frame · saw scale 60°
A flat frame is simply 180 divided by the number of sides. A sloped-sided box is not: both the mitre and the bevel change together with the slope, and setting one correctly while leaving the other at the flat value opens every joint on the outside. Errors multiply by the number of joints. Half a degree of error on a four-sided frame closes to a two-degree gap; on a twelve-sided one it becomes six. Cutting a test set from offcuts costs minutes and saves the material. Most mitre saws are marked from 90° to the fence rather than from the workpiece, which is why the saw setting and the mitre angle are different numbers for anything other than a square frame.
How the Mitre Angle Calculator works
Mitre and bevel angles for any number of sides, flat or sloped, with the saw scale reading and the shape's across-flats and across-corners dimensions. Compound cuts move both angles together.
Also known as: what angle to cut a hexagon · compound mitre for sloped sides · mitre saw angle for a polygon · why does my mitre frame have gaps
Frequently asked questions
What angle do I cut for a hexagon?
30° on each end — 180 divided by six. The general rule for any flat frame is 180 divided by the number of sides.
What is a compound mitre?
A cut with both a mitre and a blade tilt, needed when the sides slope rather than standing vertical. Both angles change together with the slope.
Why does my frame have gaps?
Usually accumulated error. Half a degree on a four-sided frame closes to a two-degree gap; on a twelve-sided one it becomes six. Cut a test set from offcuts first.
Why is the saw setting different from the mitre angle?
Most mitre saws are marked from 90° to the fence rather than from the workpiece, so the scale reads the complement for anything other than a square frame.
Can I cut a compound mitre with one setting?
No. Setting the mitre correctly and leaving the blade vertical opens every joint on the outside face — the classic failure on a sloped planter or a crown moulding.
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