Not sure exactly what I said, or the context, but I think I remember the discussion, and I was using a very bad measuring tool at the time. I just remeasured and my cabinet is 19 1/2" inside, from inner back to front edge, so about 20" overall. If I measure the side of the microwave, it's 18", but there may be a bumped out area on the back that makes it deeper...However, right now, it's sitting almost 1/2" behind the face of the cabinet, not counting the knob.

I found my clearance specs online, but was unable to find similar info for other microwaves online, so it's apparently dependent on what each manufacturer decides.

Mine is a monstrous microwave compared to most. I know you may end up wanting one that size some day, since you want a large family, but you also may do fine with the next size down... I think you would be 'safe' with the 27" width and an 18" deep shelf, since even mine could sit on a shelf that size, as long as I didn't mind the microwave protruding past its front. Actually, that's what we did in our last house. We had no trouble using the counter underneath...Just got used it it sticking out a bit, I guess. Our uppers were 15 or 16" deep, so the shelf wasn't too much past those.

Thanks rhome!

Anyone else know where to find the required clearances of MW's?

Would love to hear from others the size (length, width, depth) of your MW shelf.

Thanks again.

Echoing rhome, I'd "google" the MW your considering and if the manufacturer doesn't have the spec, more than likely another will.