Miter Angle Calculator — Frame & Corner Cuts
Find the exact saw angle to cut for any corner joint. Enter the interior corner angle for a custom joint — or choose the number of sides for a regular polygon frame (square, hexagon, octagon …). The result is the blade angle to set on your mitre saw.
Calculation mode
°
Set your saw or mitre box to this angle from the fence/face
- 1
Corner angle
90The interior angle where the two pieces meet — each piece is cut at half this angle. - 2
Miter cut angle
90 ÷ 2 = 45
How does this calculator work?
Each piece of a corner joint needs a cut of θ/2, where θ is the interior corner angle. For a standard 90° corner that is 45°; for a regular N-sided frame it is 180°/N (e.g. 30° for a hexagon). Set your mitre saw to this angle and cut each piece symmetrically.
Formula
How this is calculated
When two pieces of wood (or trim, or frame material) meet at a corner, each piece must be cut at the same angle from a straight-cut face so that the two angled cuts mate cleanly. This cut is called a miter. For a corner where the interior angle is θ, each piece is cut at θ/2 from the face — so both cuts together span the full angle.
For a regular polygon frame (like a picture frame, an octagonal mirror, or a decorative ring), every corner has the same interior angle: (N − 2) × 180° / N, where N is the number of sides. Each miter cut is therefore 180°/N. A square frame (N = 4) needs 45° cuts; a hexagonal frame (N = 6) needs 30° cuts; an octagonal frame (N = 8) needs 22.5° cuts.
The "saw setting" value is the angle you dial into a mitre saw or set in a mitre box — measured from the fence (perpendicular to the cut face). Both pieces must be cut the same way but mirrored, so set the saw once and flip each piece rather than changing the angle between cuts.
Frequently asked questions
A square or rectangular frame has four 90° corners, so each piece is cut at 45°. On a mitre saw, set the blade to 45° and cut both ends of each piece with the same setting, flipping the piece between cuts to get a mirror image.
Measure the interior angle of the corner (for example, use a digital angle gauge or a sliding bevel on the wall). Divide that angle by 2 — that is the miter cut for each piece. For a 135° obtuse corner, each piece is cut at 67.5°.
Common causes: (1) the interior corner was measured incorrectly — walls and surfaces are rarely perfectly square; (2) the saw blade is not exactly at the set angle (check with a reliable square); (3) the two cuts were both made the same way instead of mirrored. Sneak up on the angle with test cuts in scrap material.
Also known as
TG we-Calculate Editorial Team. (2026). Miter Angle Calculator — Frame & Corner Cuts [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/miter-angle-calculator
TG we-Calculate Editorial Team. "Miter Angle Calculator — Frame & Corner Cuts." TG we-Calculate. 2026. https://we-calculate.com/calculator/miter-angle-calculator.
TG we-Calculate Editorial Team, "Miter Angle Calculator — Frame & Corner Cuts," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/miter-angle-calculator
@misc{wecalculate_miter_angle_calculator, title = {Miter Angle Calculator — Frame & Corner Cuts}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/miter-angle-calculator}}, year = {2026}, note = {TG we-Calculate} }
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