Get perfect corners every time. Enter the number of sides for a frame or box, or a specific corner angle, and get the exact miter angle to cut on each piece plus the miter saw setting.
What are you building?
How the math works
Miter angle = 90 − (180 ÷ n) · Saw setting = 180 ÷ n
Check it against the frame you know: a picture frame has 4 sides, so the saw setting is 180 ÷ 4 = 45°. A hexagon (6 sides) needs a 30° saw setting, and an octagon (8 sides) needs 22.5°.
Tips for perfect miters
- Cut all four sides with the same setup. Never move the saw between cuts for one frame — tiny changes stack into a visible gap.
- Opposite sides must be exactly equal. A perfect 45° still gaps if one side is 1 mm longer. Use a stop block.
- Creep up on trim corners. Walls are rarely 90°. Cut 45°, test with two offcuts, then adjust a half-degree at a time.
- Frames are a top beginner seller. See picture frames in our guide to woodworking projects that sell, and strengthen the joint with the methods in our joinery types guide.
Frequently asked questions
What angle do I cut for a picture frame?
45° on each piece — two 45° cuts meet to form the 90° corner. Set the miter saw to 45°, or use the polygon mode above with 4 sides to confirm any frame shape.
Why does my 45° corner still have a gap?
Three usual causes: the saw’s 45° detent is slightly off (calibrate with a known square), the workpiece moved during the cut, or opposite sides are unequal lengths. Gaps on one side only usually mean length mismatch, not angle error.
What is the miter angle for an octagon?
Each piece is cut at 67.5° measured on the workpiece, which is a 22.5° setting on a miter saw. Octagons appear in planters, frames and small tables.
Does this work for crown molding?
For simple flat trim, yes. Crown molding requires compound miter and bevel angles because the molding sits at an angle to the wall — use a crown molding angle chart or a dedicated calculator for those cuts.