http://www.fit36.com/archives/how-much-does-a-pushup-weigh/

Given that I’m doing the 100 Pushups Challenge, this is an interesting question. The answer in the article is 65-75%.

Interestingly enough, the Flying Pig in Cincinnati has an associated event (for the 5k, 10, half and full) Pump and Run. The benchmark weight for a 19-39 year old male is 75% of body weight.