How to Use Miter Angle Calculator
The Miter Angle Calculator is the saw setup tool every finish carpenter wants on hand.
- Pick a mode — Corner, polygon or compound.
- Enter the geometry — Corner angle, side count, or spring + corner angle.
- Read the result — Per-piece miter angle, saw setting and (for compound) bevel angle.
Formula & Theory — Miter Angle Calculator
The Miter Angle Calculator uses three small formulas:
Corner: miter = θ / 2, saw = 90° - θ / 2
Polygon: θ = 180° × (n - 2) / n
Compound: miter = arctan(sin(spring) × tan(θ / 2))
bevel = arcsin(cos(spring) × sin(θ / 2))| Symbol | Meaning |
|---|---|
| θ | Inside corner angle |
| n | Number of polygon sides |
| spring | Slope angle of moulding off the wall |
Compound geometry
For a 38° spring crown joining at a 90° corner, the miter angle is about 31.6° and the bevel about 33.9°. The Miter Angle Calculator handles non-standard spring angles too.
Use Cases for Miter Angle Calculator
- Trim carpentry — Set up crown, base and casing on a single corner or full room.
- Picture framing — Find the cut angle for any custom polygon.
- Furniture building — Lay out hexagonal, octagonal or other shaped tables.
- Cabinet making — Match faces and toe-kicks at irregular angles.
- Roof framing — Determine miter and bevel for sloped fascia returns.
- Education — Demonstrate the relationship between regular polygons and miter cuts.
The Miter Angle Calculator is a workshop and classroom essential for tight, repeatable joinery.