Back to workshop tools
Free woodworking tool

Mitre Angle Calculator

Calculate the correct mitre cut angle for frames, boxes, trim and multi-sided woodworking projects. Use Corner Joint for standard corners, or Equal-Sided Shape for pentagons, hexagons, octagons and other regular layouts.

Frames and trim Polygon builds Fast cut reference Visual cut guide

When this helps most

Use this tool when building picture frames, planter boxes, trim corners, pentagonal and octagonal projects, polygon shelves, or any equal-sided shape where accurate mitre cuts matter for a clean joint.

Calculate your mitre cut

Choose the method that matches your project. Corner Joint works for standard corners. Equal-Sided Shape works for regular shapes such as pentagons, hexagons and octagons.

Results are shown in degrees. This tool assumes a standard two-piece mitre joint.

deg

This is the full finished corner angle. Example: a square corner is 90 deg.

Cut result

Your cut values and visual guide update here after calculation.

Visual guide
Corner joint view
Shape Corner joint
Joint angle -
Cut per piece -
Mitre cut angle per piece
-
Joint angle
-
Pieces meeting at joint
2
Enter a corner angle or number of sides, then click Calculate to see the correct mitre cut for each piece.
Always confirm your saw orientation and make a test cut before cutting final stock.

How this works

For a standard mitre joint, each piece is cut to half of the full joint angle. For regular shapes, the tool first finds the interior angle, then divides it by two.

Common examples

90 deg corner = 45 deg cuts. 120 deg corner = 60 deg cuts. A pentagon uses 54 deg cuts. A hexagon uses 60 deg cuts. An octagon uses 67.5 deg cuts.

Best use cases

Picture frames, trim work, planter boxes, polygon shelves, decorative boxes, and segmented woodworking layouts.