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Woodshop Miter Angle Calculator

Calculate miter and bevel angles for multi-sided frames, boxes, and crown molding. Find saw settings for hexagons, octagons, and compound cuts.

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Number of Sides
Output to expect
Miter Angle Calculator
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  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Simple Miter Angle

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 and Exterior Angles

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° / N

Compound Miter for Crown Molding

Crown 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

Example Scenarios

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.

Common Mistakes to Avoid

Using 360/N instead of 180/N for miter 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.

Ignoring spring angle when cutting crown molding

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.

FAQ

A regular hexagon uses 30° miter cuts on each end. Set your saw to 30° and cut equal-length pieces — six pieces form a closed hexagon with 120° interior corners.

Gaps usually come from pieces being slightly different lengths, saw not set exactly to 45°, or blade deflection. Test with scrap and verify the saw angle with a digital protractor.

Use compound settings for both miter and bevel. For 52°/38° crown on a 90° corner, typical flat-nesting settings are ~31.6° miter and ~33.9° bevel for inside corners.

A regular pentagon uses 36° miter cuts (180°/5). Interior angles are 108°, so each cut removes 36° from the end of each piece.

Simple four-sided frames need only a basic miter saw at 45°. Compound saws are needed for crown molding, sloped boxes, or any joint where pieces meet at non-90° three-dimensional angles.

About Woodshop Miter Angle Calculator

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.