Miter angle calculator
For flat trim — baseboard, door casing, chair rail nailed flat to the wall. Enter the corner angle and this halves it for you: no bevel, unlike crown molding, because flat trim never leaves the plane of the wall.
°
90 for a square corner, measured with a protractor otherwise
Miter each piece at
45.0°
Bevel
0°
About mitering flat trim
- What angle do I cut baseboard or casing for a corner?
- Half the corner angle. A square 90° corner miters at 45° on each piece; an open 135° corner — common where a bay or an addition meets the original wall at an angle — miters at 22.5°.
- Why doesn't this need a bevel setting like the crown molding calculator?
- Crown leans out from the wall, bridging it to the ceiling, so cutting it flat on the saw table needs a miter and a bevel together. Baseboard, casing and chair rail nailed flat never leave the plane of the wall — the joint is only ever a miter, and the bevel stays at zero the whole time.
- How do I find my actual corner angle?
- A digital angle finder reads it directly. Without one, hold a scrap of scrap trim in the corner as if it were the actual pieces, mark where the two overlap, and the angle between those marks — measured with a protractor or a speed square — is the corner. Most walls are close to 90°, but 'close' still shows up as a visible gap at the point of the miter.
You might also need
- Baseboard calculatorLinear footage of flat trim for a room from its perimeter and its doorways, with a waste allowance.
- Crown molding anglesThe miter and bevel for any corner and any spring angle, plus the single setting for cutting it nested.
- 3-4-5 square checkThe diagonal that proves a corner square from any two leg lengths, scaled up for a full building corner.