Mitered angles are a basic element carpentry used to join pieced of wood trim where two angles come together. The proper cut depends on calculating the angel correctly. A simple mathematical method will determine the miter cut needed for any angle.
Place a bevel square against the two adjacent wall planes at the corner. Tighten the bevel square's locking screw to hold the setting.
Align the base of a protractor with the edge of the bevel square's hand. Read the protractor's degree scale where the bevel square's blade crosses it to determine the angle.
Define the miter cut angle by dividing the angle determined in Step 2 by two. Example: the miter cut angle for a 90-degree corner is two 45-degree angles. Use this basic formula to calculate the mitre cut for any corner or angled joint.