C.K.
I think it's 40 #, and you can put him on your back when he's too heavy for the front. My son was a pretty big baby, but he really slowed down on weight gain as a toddler, so he's just now reaching 40# at his 4th birthday. So it took him three years to go from 25 to 40 pounds, plenty of time to get my money's worth out of the Ergo. I guess a better question is how long you'll be ABLE to carry him if he's such a big guy.