Measure the depth and length of the cabinets where you want to hang the microwave. Measure the distance between the top of the counter and the part of the cabinet where you'll install the microwave; many cabinets hang 30 inches above the counter, which allows plenty of space to stir pots on the range.
Measure the width, depth and height of the microwave with a tape measure. Check the outside of the product box for exact measurements.
Compare the microwave measurements to the space available on your counter or under your cabinets. Keep in mind that hanging range units are commonly taller than traditional countertop microwaves to accommodate a fan and light.