FreeMiter Angle Calculator
Choose the number of sides of a frame, or the angle of a corner, and get the setting for your miter saw, the angle on each piece and, for a frame, the long-point length to cut every side from the inside size and the width of the moulding.
Frame or corner
- Miter saw setting
- 30°
- Angle on the piece
- 60°
- Inside angle of the frame
- 120°
- Each piece, long point
- 12 5/16"
Cut 6 pieces, both ends at 30° on the miter saw, pointing in opposite directions. Measure each piece from long point to long point.
- Choose a frame with equal sides, or a single corner.
- Type the number of sides (or the corner angle), and for a frame its inside side length and the moulding width.
- Set the saw to the miter angle and cut each piece to the long-point length.
Miter angle chart
| Frame | Sides | Miter saw setting | Angle on the piece | Inside angle |
|---|---|---|---|---|
| Triangle | 3 | 60° | 30° | 60° |
| Square or rectangle | 4 | 45° | 45° | 90° |
| Pentagon | 5 | 36° | 54° | 108° |
| Hexagon | 6 | 30° | 60° | 120° |
| Heptagon | 7 | 25.71° | 64.29° | 128.57° |
| Octagon | 8 | 22.5° | 67.5° | 135° |
| Nonagon | 9 | 20° | 70° | 140° |
| Decagon | 10 | 18° | 72° | 144° |
| Hendecagon | 11 | 16.36° | 73.64° | 147.27° |
| Dodecagon | 12 | 15° | 75° | 150° |
How to find a miter angle
For a frame with equal sides, divide 180 by the number of sides: 45° for a square, 30° for a hexagon, 22.5° for an octagon. For a single corner, take the corner angle from 180 and halve it: two pieces meeting at 135° are each cut at 22.5°.
Most miter saws read 0° for a square cut, and that is the setting given here. The angle left on the piece, measured from its edge, is 90° minus that setting.
Cutting a frame
Measure each piece from long point to long point: the outside edge. It is the inside length plus twice the moulding width × tan(180° ÷ sides): for a square frame, the inside length plus twice the width. Cut one test frame from scrap first; a tenth of a degree on each of eight cuts leaves a visible gap.
Start from a furniture plan instead
All plans →Do not want to work out every part? Pick a design, type its size and get the cut list.
Frequently asked questions
What angle do I cut for an octagon?
22.5° on the miter saw for each end of all eight pieces (180 ÷ 8).
What angle do I cut for a hexagon?
30° on the miter saw (180 ÷ 6); the frame has inside angles of 120°.
What is the miter angle formula?
180 ÷ number of sides for a frame; (180 − corner angle) ÷ 2 for one corner.
How do I miter an outside corner that is not 90°?
Measure the corner with an angle finder, take it from 180 and halve it. A 135° bay corner takes 22.5° on each piece.
Learn more
Types of SawsThe main types of saws for wood: power saws (circular, table, miter, track, jigsaw, band) and hand saws, what each one cuts best, and which saws to buy first.Types of Wood JointsThe main types of wood joints explained: butt, rabbet, dado, dowel, biscuit, pocket hole, mortise and tenon, dovetail, and which to use in plywood and MDF.