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A6 · Woodworking calculator

Compound Mitre Calculator for Cornice & Crown Moulding

For sprung cornice, coving or crown moulding cut flat on a mitre saw table, convert the included wall corner and spring angle into mitre and bevel angles. Check left or right direction on your own machine.

Free to use · no account needed · calculations stay in this browser · formula reviewed 4 September 2026

Enter the moulding geometry

This calculator is only for sprung cornice or crown moulding laid flat on the saw table. Measure the actual included wall corner. The spring angle is measured from the wall to the back of the moulding at its intended wall-contact edge.

°
°

Flat method: mitre = atan(sin(spring) ÷ tan(corner ÷ 2)); bevel = asin(cos(spring) × cos(corner ÷ 2)). Results show positive angle values, not left or right cut directions.

Example result using the values shown

Mitre angle — direction not shown
31.62°
Bevel angle — direction not shown
33.86°
Half of included corner
45.00°
Method
Flat on table

Angle values only. Establish the reference face, left or right direction and waste side from your saw manual, then test a pair of scraps.

  • 90° included inside corner; 38° spring angle.
  • Moulding lies flat; values use 0° for a square mitre and vertical blade.

Why this is separate from an ordinary mitre

A sprung profile meets the corner while tilted away from the saw table. That couples the table rotation and blade tilt, so simply halving the wall angle is not enough.

Inside versus outside changes workpiece orientation and waste side, not these two angle values. Saw scales and bevel direction vary.

Worked example

A 90° included corner with a 38° spring angle returns a 31.62° mitre angle and 33.86° bevel angle. A two-piece scrap test remains part of the method because real corners, profile seating and machine scales can differ.