Construction Calculators

Miter Angle Calculator

Calculate the miter cut angle needed to join the corners of a regular multi-sided frame, such as crown molding or a picture frame.

Miter angle (per cut) —

Interior corner angle —

About the Miter Angle Calculator

This calculator finds the miter saw angle needed to join the corners of a regular multi-sided frame or shape, such as a picture frame, planter box or crown molding running around a room.

Formula: Miter Angle = 180° ÷ Number of Sides. For a standard 4-sided rectangular frame, that's 180 ÷ 4 = 45° per cut, the most common miter setting.

Set your miter saw to the calculated angle for each of the two boards meeting at a corner — together they form the full interior angle. Always cut a test piece first, since real-world corners are rarely perfectly square.