Miter Angle Calculator
Every side of a frame shares the error, so a fraction of a degree becomes a visible gap. Get the exact saw angle for any number of sides — or any custom corner — and know before you cut, not after.
3 = triangle, 4 = square/rectangle, 6 = hexagon, 8 = octagon. Any number works.
Adds total stock length. For full cut lengths with rabbets, use the Picture Frame calculator.
90° for a square corner. The angle the two finished pieces form.
Formula & how it works
For a regular frame of N sides, each miter (the saw angle from square) is 180 ÷ N, and the joint the two pieces form is the interior angle (N − 2) × 180 ÷ N.
For any corner angle θ, the saw angle is 90 − θ ÷ 2 when the joint is split equally. An unequal split keeps the two miters adding to 180 − θ so the corner still closes.
Worked example
A hexagonal frame has 6 sides: each miter is 180 ÷ 6 = 30°, the joints are 120°, and you make 12 cuts (two per side). An octagon drops to 180 ÷ 8 = 22.5°.
Cutting clean miters
Equal-length sides matter as much as the angle
Even with a perfect angle, a frame will not close if opposite sides differ in length. Cut matching pieces with a stop block so every pair is identical, and the angles have a fair chance of meeting.
Common frame angles
Square and rectangle frames are 45°, pentagons 36°, hexagons 30°, octagons 22.5°, and twelve-sided rings 15°. Odd shapes are no harder — the saw angle is still 180 divided by the number of sides.
Test before you commit
Miter scales on saws drift, and a half-degree spread over many cuts leaves a gap. Cut a few scrap corners, dry-fit them, and nudge the saw until the joints close before touching your good stock.