It'll fit the salesman said, they're all standard size to fit the typical opening for a mounted microwave, you'll have no problem. Don't worry about the dimensions and it's in stock. So we bought it and carried it home. It was heavy, it was awkward, Mac called our friend to come and help. I was cooking beans, they said not to worry, twenty minutes tops to get the old one out and the new one in.
Two and a half hours later it was done. I don't know what standard size is, but it's not what we have. The holes for the screws that hold it in place were in a different place, the microwave itself was deeper than our old one, it sticks out a bit. Because it's over the stove that's not a problem, but it definitely isn't the same size as our old one.
I can only assume that the salesman in search of a sale had no idea what he was talking about or that he's never installed a microwave or standard size is a a mythical number. The store charges $75.00 to install a microwave , we now know why.
But it does pop popcorn.