How much weight of a whole life chicken is a supermarket whole chicken?
Broiler chickens, at least in the US, are bred to grow quickly.  They are usually slaughtered when then weigh about 4 pounds, which is at about 7 to 9 weeks.  In general, a grocery store broiler weighs about 3 to 3.5 pounds.  As the comments above suggest, this is a very general response.  It would be difficult to be more accurate.