How long should a changing table be?

I'm looking at buying a changing table for our new baby, but the ones I'm looking at online seem like they would be too short. I mean the length of the table top.. Most seem to be only 20-22 inches long, and aren't most babies almost that long when they're born? I found a couple that were about 27-28 inches long, and an oversized one that was 47. How big is yours and does it seem long enough?