Miter Angle Finder

Start by measuring the actual corner, not the corner you expect. Place a protractor or a bevel gauge against the inside corner and read the angle, then divide by two for the miter. For outside corners, measure the angle of the outside face - it is the supplementary reference of the inside corner, so confirm which surface you are reading before you cut.

Cut both pieces at the same miter angle. A common mistake is to cut one piece at the miter and the other at its complement; that only works when the corner is exactly 90°. For any other corner, symmetry is what closes the joint: each piece carries half of the corner, and the two halves add up to the corner.

Crown molding adds a second angle - the bevel - because it sits at an angle to the wall as well as in the plane of the wall. Flat-cut crown uses a miter plus a spring angle (typically 38° or 45°), while nested crown is cut with the molding lying against the fence. The miter angle itself is still half the corner; only the bevel changes with the installation method.

Practical tips: make a test cut on scrap first, cut the long pieces slightly over-length so you can fine-tune, and use a sharp blade - a ragged edge looks like a bad angle even when the geometry is right. For picture frames, cut four pieces at half the corner angle (45° for a rectangular frame) and check the frame diagonals; equal diagonals confirm the frame is square.

If you are working from a photo or a plan rather than the physical corner, overlay the digital protractor on the image, align the baseline with one wall and read where the second wall falls. Then divide that reading by two here. This is especially useful for corners you cannot reach, such as a second-storey return or a built-in unit.