How to Measure and Cut Trim Angles

How to Cut Molding and Make Perfect Mitered Corners

Introduction:

When installing trim it can be difficult to obtain perfectly matched mitered corners because walls are rarely square. Simply cutting two pieces of adjoining trim at a 45 degree angle frequently does not give you a perfectly fit corner. Frequently the results will be that there is a space between the two trim pieces that will always remain visible and appear as though an amateur did the trim work.

This problem is easily solved. The DIY homeowner can measure and cut angles for any piece of trim and get a perfect joint. One or two tools are required that can be purchased at any home improvement supply center. You only need two tools for measuring angles, a carpenter’s bevel square and a protractor. These tools can be purchased for under $10 each.

A carpenter’s bevel square is similar to a traditional combination square however with the bevel square you can adjust the length of one of the arms and rotate it to any position. With these features you can use the bevel square to determine the exact angle of any corner and make perfect trim joints.

To measure an outside angle for baseboard trim place one of the arms of the bevel square up against one of the wall surfaces, and then rotate the other arm until it is flush with the adjacent wall. Then tighten the wing nut on the bevel square.

Place the bevel square up against the protractor and read the angle measurement off of the protractor. Then divide the angle measured by two to determine the setting on your miter saw. For example if you measured 86 degrees on the carpenter’s bevel square, divide this number by two. The result (43 degrees) is the angle measurement setting on the miter saw. After cutting each piece of trim at a 43 degrees angle they will make the joint fit perfectly.

For measuring angles for trim on inside corners the process is the same. Place the carpenter’s bevel square up against the inside corner and spread the arms until each arm is flush with its respective wall surface. Tighten the wing nut and measure the angle using the protractor. Again, divide the angle measurement by two and set the miter saw to this angle. Cut each piece of trim and place them against the walls to confirm that you have formed the perfect inside corner joint.

That is all there is to it. Now you can make perfect inside and outside mitered corners.

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