Measure each radiator dimension as shown here, using a metal tape measure. For best heating efficiency, you should allow at least 1/2" to 1" between the radiator and the enclosure to permit sufficient airflow. Then go to the next LARGER of each of our stock sizes, and check to make sure this size fits into your area
For the width, measure as shown, including any pipes or valves that need to be enclosed.
Measure from the floor to the top of the radiator, taking note of any window sills that may interfere with the enclosure.
For Depth, measure from the front of the radiator, to either the back of the radiator, or the wall/baseboard, depending on your preference.