Miter Angle Calculator

Building a picture frame, planter box or any equal-sided polygon? This finds the exact miter angle to set your saw for tight corners.

How the Math Works

The Miter Angle Calculator uses the polygon interior angle formula to determine precise cut angles. For any polygon with n sides, the interior angle is calculated as interior = 180 × (n − 2) ÷ n, which represents the angle inside the shape at each vertex. The miter cut angle is then derived as miter = 90 × (n − 2) ÷ n, representing half the interior angle since each miter cut bisects the corner. This relationship works because when two pieces meet at a corner, each piece must contribute half the interior angle to form the complete angle.

Practical Applications

To use this calculator practically, first determine how many sides your polygon frame requires (n). Enter this value into the calculator to get the miter angle. When cutting your material—whether wood, metal, or plastic—set your miter saw or protractor to this exact angle. Each piece should be cut identically, and when joined, the two cut edges will form the perfect corner angle. Always measure twice and cut once, and remember to account for material thickness in your layout before making cuts.

Day-to-Day Use

This calculator solves real-world problems in DIY projects and professional work. Whether you're building a picture frame, installing crown molding, creating a decorative wreath, or constructing a garden planter, knowing the exact miter angle ensures clean, professional-looking joints without gaps. It prevents costly mistakes that waste materials and eliminates the need for time-consuming trial-and-error cutting. From weekend woodworking projects to professional carpentry, this tool helps you achieve precise results that would be difficult to calculate mentally while holding a saw.

Worked example

A 4-sided frame → interior 90°, miter 45° per cut. A hexagon (6 sides) → interior 120°, miter 60°.

FAQ