Compound Miter Angle Calculator
General miter tool: polygon frames by side count, corners by angle, and a crown/compound mode with bevel — beyond the simple corner-only miter tool.
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What this tool does
General miter tool: polygon frames by side count, corners by angle, and a crown/compound mode with bevel — beyond the simple corner-only miter tool. Saw settings are magnitudes measured from a square crosscut, with both pieces cut equally. How this differs: the existing Miter Angle Calculator handles one equal corner only, and the Crown Molding Angle Calculator is crown-only — this tool unifies polygon frames (hexagon tables, planters, frames) with corner and crown-compound modes in one place.
How to use the Compound Miter Angle Calculator
- Enter or select mode.
- Enter or select number of sides (polygon mode).
- Enter or select interior corner angle (degrees).
- Enter or select spring angle (degrees, crown mode).
- Read the calculated result; change any measurement to compare alternatives.
Formula
polygon: interior angle = (sides − 2) × 180 / sides; miter setting = (180 − interior angle) / 2; crown: miter = atan(sin(spring) / tan(corner/2)), bevel = asin(cos(spring) × cos(corner/2))
- mode
- Mode
- sides
- Number of sides (polygon mode)
- cornerA
- Interior corner angle (degrees)
- springA
- Spring angle (degrees, crown mode)
Saw settings are magnitudes measured from a square crosscut, with both pieces cut equally. How this differs: the existing Miter Angle Calculator handles one equal corner only, and the Crown Molding Angle Calculator is crown-only — this tool unifies polygon frames (hexagon tables, planters, frames) with corner and crown-compound modes in one place.
Worked example
For compound miter angle calculator, the following measurements illustrate the exact method: Mode: polygon; Number of sides (polygon mode): 6; Interior corner angle (degrees): 90; Spring angle (degrees, crown mode): 38.
Inputs
- ModeRegular polygon / picture frame (by number of sides)
- Number of sides (polygon mode)6
- Interior corner angle (degrees)90
- Spring angle (degrees, crown mode)38
Result
- Miter saw setting (degrees)30
- Interior angle (degrees)120
- Included angle between pieces (degrees)60
Results explained
- Miter saw setting (degrees)
- Miter saw setting (degrees) from the formula above. Saw settings are magnitudes measured from a square crosscut, with both pieces cut equally. How this differs: the existing Miter Angle Calculator handles one equal corner only, and the Crown Molding Angle Calculator is crown-only — this tool unifies polygon frames (hexagon tables, planters, frames) with corner and crown-compound modes in one place.
- Interior angle (degrees)
- Interior angle (degrees) from the formula above. Saw settings are magnitudes measured from a square crosscut, with both pieces cut equally. How this differs: the existing Miter Angle Calculator handles one equal corner only, and the Crown Molding Angle Calculator is crown-only — this tool unifies polygon frames (hexagon tables, planters, frames) with corner and crown-compound modes in one place.
- Included angle between pieces (degrees)
- Included angle between pieces (degrees) from the formula above. Saw settings are magnitudes measured from a square crosscut, with both pieces cut equally. How this differs: the existing Miter Angle Calculator handles one equal corner only, and the Crown Molding Angle Calculator is crown-only — this tool unifies polygon frames (hexagon tables, planters, frames) with corner and crown-compound modes in one place.
Frequently asked questions
A regular hexagon's interior angle is 120°, so each piece is cut at (180 − 120) / 2 = 30° on the miter saw. An octagon (135° interior) needs 22.5°.
A rectangular frame is a 4-sided polygon: interior 90°, miter setting 45° — the familiar picture-frame cut. A 5-sided frame needs 36°, a 6-sided 30°.
The Miter Angle Calculator takes a single corner angle only; the Crown Molding Angle Calculator does crown compound cuts only. This tool adds the polygon-by-sides mode woodworkers actually use for frames, planters and segmented work, and includes the crown mode alongside.
Crown sits tilted (the spring angle) between wall and ceiling, so a flat-laid cut is a compound angle: the miter and bevel combine to produce the corner. Nested cutting (molding held at its spring angle) needs only the miter — use the corner mode with the crown held in position.
Measure the real corner with a digital angle finder and use corner mode with the measured angle. A 92° corner wants a 44° setting, not 45°, and that 1° is the gap you used to fill with caulk.