Miter Angle Calculator

What angle do I cut for a miter?

deg
in
in

Set your saw to

45°miter

For a flat miter with the same angle on both boards. Cut a test pair, because few corners are exactly what you measured.

Corner 90 degreesSaw at 45 degrees3.5 in wide boards
Corner angle90 degrees
Inside length of each piece3 ft 5 in
Pieces for a closed shape4

Enter a corner angle and see the miter saw setting and the inside length of your pieces.

How it works

A flat miter is half of 180 minus the corner angle, so a 90 degree corner cuts at 45.

Before you order

  • Measure real corners with a bevel gauge, because walls are rarely square.
  • Cut long, then creep up to the line.
  • Rub a little glue into end grain before fastening.

Common questions

What angle for an octagon?

22.5 degrees on each end, for a 135 degree corner.

What is the inside length?

The short edge of a mitered piece, shorter than the outside by twice the width times the tangent of the miter.