How to Calculate Miter Cuts on a Handrail

Lay your handrail diagram with angles in a large room or garage and draw it on the floor. Draw one angle at a time.

Measure the handrail width. Now cut two pieces of plywood that size, likely two to two-and-a-half inches wide by 48 inches long. Lay out the plywood strips, aligning them with your sketched handrail system. Allow one end of the strip to overlap the other end directly above the angle you wish to calculate.

Eyeball the degree of the angle by standing above it, then take a pencil and draw a line through where you think the angle should be. Pick up the strips and take them over to the miter saw.

Loosen the dial on the miter saw and swing the blade directly over your mark on the strip. Bring the blade down until it's aligned with the mark. Lock down the dial, turn on the saw and cut the end of both plywood strips at this angle.

Place the strips back down on the floor, aligning them with the handrail drawing. Bring the angles together, measure the gap and divide by half. Re-set the miter saw by half in the direction needed. Re-cut both pieces. If you still have a gap, repeat until the angle closes and the 48-inch strips are perfectly aligned with your drawing. This is your angle. Write it on the end of the strips, top and bottom. Draw out your next angle on the floor and repeat the steps.