You will get a range of estimates - from 4 to 15 (or even 35) years.
From the Glasgow zoo:
"3. The 'natural' lifespan of a chicken could be over 12 years.
However, even in the wild they are predated upon by everything. An
'oldish' chicken looks like that and is likely to be selectively
picked out by a predator, plus its reactions will be slowing down. One
of our hens here, 'Rambo', is over eight years already and still
"Broiler chickens are slaughtered after just six or seven weeks (a
chicken's natural lifespan is around seven years)."
The site below talks about a specific chicken regarded somewhat as a pet.
"According to The Chicken Health Handbook by Gail Damerow, the maximum
lifespan of a chicken is 30-35 years. If that is true, we'll take it!"
"While chickens produce eggs, most owners grow to consider them as
pets. The average lifespan of a chicken is eight to 10 years, so when
considering adding hens to your family, plan your commitment
"Chickens and ducks can live anywhere from 5 - 10 years depending on
the quality of life provided. Most hens stop laying eggs around 3
years of age."
"The natural lifespan of a chicken is about ten years."
"The natural lifespan of a chicken ranges from 7-20 years."
"The lifespan of a chicken is 15 years. "
" Did i mention the average lifespan of a chicken is four to six years and these
guys live one year in horible conditions"
"Average Lifespan: 13 year(s)" (This is in regard to the Silkie Bantam.)
"Pet chickens average lifespan is about 15 years."
"Lifespan: 8-10 years" (This is for Cochin chickens.)
Oops! I just tried to post this and it was locked while I was
composing this. Anyway, you'll have something for comparison when the
question is open again. (I knew better than to even start answering,
but I was just interested - probably an aftereffect of a show I once
saw on TV entitled something like "The Natural History of the
Chicken." It was a riot.)