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For regular polygons where pieces meet flat, each miter is half the interior angle between adjacent sides.
Miter = 180° / N (where N = number of sides)Interior angle of a regular N-gon equals (N−2)×180°/N. The miter cut is half the supplement of the interior angle, which simplifies to 180°/N.
Interior angle = (N − 2) × 180° / NCrown sits at a spring angle (typically 38° or 45°) against the wall and ceiling. Compound miter requires both miter and bevel settings derived from the wall angle and spring angle.
Bevel = arctan(sin(Miter) × tan(Spring))Updated: July 2026
Six-sided box requires miter cuts at 30° on each end (180°/6). Each piece meets its neighbor at 120° interior angle for a closed hexagon.
Eight-sided frame needs 22.5° miter cuts (180°/8). Set miter saw to 22.5° left and right for alternating pieces.
Standard 52°/38° crown on a 90° inside corner uses miter 31.6° and bevel 33.9° on the saw (flat method) or 45° miter with crown nested at spring angle.
The miter saw setting is half the corner angle: 180° divided by number of sides. Using 360/N gives the full corner angle, not the cut angle, and produces open joints.
Crown is not cut at 45° miter when nested at its spring angle. Use crown-specific angle charts or this calculator that accounts for the 38° or 45° wall-to-ceiling orientation.
Cutting accurate miters for polygons, picture frames, and crown molding requires more than dividing 90° by the number of sides. This calculator provides miter saw settings for simple and compound angles for boxes, frames, and trim work.