How old are they all in 2016?

Well, I just watched the episode where Sheldon sets up online dating for Penny and she tells him that she is 22. - This was season 2

In the episode where Sheldon gets fired, in season 1, he says that he worked 3,5 at the university, before that he worked 4 years on his these, was in college and even before that in 5th grade. I think it was stated somewhere that he started university when he was 11, so 11+4+4+3.5 would be about 22.5 years in season 1.

Leonard said he got his PHD when he was 24, so he was at least 24 in season 1. He has is birthday episode in season 1, but I don´t think they said how old he got. I could imagine he is 25 - He already has his PHD and worked in the same job at the university.

I am not sure about Wolowitz and Raj.

I'm pretty sure the guys are all the same age (approx.) and are roughly 5 years penny's senior. There fore in Series 2 (Penny says she's 22) Penny is 22 and the guys are all around 27 and it has been said that Penny is 30 now which makes the guys 35. In real life there is 10 years between Jonny and Kaley so the chaps have been aged down.

I think Bernadette is the same as Penny whilst Amy is the same as the guys.

To you, Baldrick, the Renaissance was just something that happened to other people, wasn't it?

And note that inconsistency is an unfortunate hallmark of this show.

http://bigbangtheory.wikia.com/wiki/Sheldon_Cooper
Sheldon ... "fell out" of Mary at a K-mart in 1980.
http://bigbangtheory.wikia.com/wiki/Leonard_Hofstadter
Leonard was born on May 17, 1980 in New Jersey
http://bigbangtheory.wikia.com/wiki/Howard_Wolowitz
Howard was born in Pasadena sometime between March 1 and September 30, 1981
http://bigbangtheory.wikia.com/wiki/Rajesh_Koothrappali
Rajesh Koothrappali was born in New Delhi, India on October 6, 1981
http://bigbangtheory.wikia.com/wiki/Penny_Hofstadter
No mention of birth year that I noticed.

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Mr Smith: Like the rose trampled on the ground, you took the fall