Miter Angle Calculator
Calculate exact miter and compound bevel saw settings for out-of-square room corners, multi-sided polygon frames, and flat-laid trim.
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How Miter Saw Angles Work
Miter saw dials do not start at 90° for a square cut; they start at 0°. That means when your blade is perpendicular to the fence, your saw reads 0°. When you make a 45° corner joint, your saw is pivoted 45° away from zero.
Out-of-Square Corner Formula
Saw Angle = |90° - (Corner Angle / 2)|
Polygon Miter Formula
Saw Angle = 360° / (2 × Sides)
Common Polygon Miter Angles
- Triangle (3 sides): 60.0° saw angle (120° corner)
- Square (4 sides): 45.0° saw angle (90° corner)
- Hexagon (6 sides): 30.0° saw angle (120° corner)
- Octagon (8 sides): 22.5° saw angle (135° corner)
- Decagon (10 sides): 18.0° saw angle (144° corner)
Frequently Asked Questions
Why does drywall corner bead throw off miter angles?
Drywall tapers build up joint compound at inside and outside corners, meaning actual walls rarely measure exactly 90.0°. Most drywall corners measure 88.5° to 91.5°, causing gaps in baseboard miters if cut at exactly 45°.
Should I cope or miter inside baseboard corners?
Professional finish carpenters cope inside corners rather than mitering. Coping creates a lap joint that does not open up when wall studs expand and contract through seasonal humidity shifts.
What is the miter angle for an 8-sided octagon box?
An octagon has 8 sides totaling 360 degrees of rotation. Divide 360 by 16 (8 joints x 2 cuts per joint) to get an exact 22.5° miter saw angle.