Could you tell me a usual way to describe a three dimensional object, for example, a fridge?

This fridge is 30cm wide, 20cm --- , and 50cm high.

I know it seems strange, but we usually say "deep." (Usually, a swimming pool has depth.) This is more like the third dimension of a photograph, or painting. "The painting has depth." (the dimension "away from you")

Edit. I just double checked an industrial equipment catalog: "Wd. x Dp. x Ht."

We'd also speak of the depth of a closet, or a garage, or a cave which runs straight back into a mountain - and, of course, of a hole, regardless of orientation.

Just as an aside, it's a bit unusual to use the indefinite article with "usual," except in the negative. "This is an unusual painting," but not, "this is a usual painting." "Round up the usual suspects." This is less true of "common/uncommon" and "normal/abnormal" and "correct/incorrect."
Got it!
Thanks, Avangi.