How to Calculate Miter & Bevel Angles

Miter and bevel angles can produce great detailing in crown molding.

Crown molding adds distinction and prestige to any room in which it is installed. This architectural detailing is performed by carpenters and designers by identifying developer two beveled pieces of trim formed to create a joint (miter) and installing them against a wall or cabinetry structure. Using the dimensions of the miter and bevel angles, the carpenter can assemble a perimeter of molding that frames the subject as a crown would frame one's head -- thus the name crown molding.

Things You'll Need

• Protractor
• Miter table
• Leveler
• General scientific calculator

Instructions

1. Find the components. Determine the wall angle using the leveling tool, miter table and protractor.

2. Determine the miter angle using a general scientific calculator. Divide the wall angle by 2, find the tangent by pressing "Tan" and name the resultant X. Multiply the earlier resultant, "X," by 5.5 to obtain a new resultant, "Y." Divide 3.8 by Y, and then find the inverse tangent by pressing the "Inv" button followed by "Tan."

   For example, where the wall angle is 45 degrees, compute 45 / 2 = 22.5 and press "Tan," which equals 0.4142. Multiply 0.4142 x 5.5 = 2.278. Divide 3.88 by 2.278, which equals = 1.703. Press "Inv" "Tan," which equals 59.58 degrees.

3. Calculate the bevel angle. Divide the wall angle by 2, and then determine the cosine by pressing "Cos". The resultant is X. Multiply X times 3.88, and the resultant is Y. Divide Y by 5.5, and then determine the inverse tangent by pressing "Inv" then "Tan".

   For example, where the wall angle is 45 degrees, compute 45 / 2 = 22.5 and then press "Cos," which equals 0.9238. Multiply 0.9238x 3.88 = 3.584. Divide 3.584 by 5.5, which equals =0.6516. Press "Inv" "Tan," which equals 33.08 degrees.

References

• Alter Eagle; How to Install Crown Molding; 2011