Altair and Desmond were 6'0 (183cm) and Ezio was around 5'10.
The developers did say in the Inside AC3 videos he was heavier and bulkier than previous protagonists who they described as 'small guys in lots of armor'.
From playing the game my guess would be around 6'2. He doesn't look like someone who is shorter than or 6'0. Also the natives who lived around New York/Canada were described as very tall people.
Conor Kenway, the protagonist of "Assassin's Creed III," is depicted as being approximately 6 feet tall (183 cm). His height, along with his athletic build, complements his skills as an assassin in the game's historical setting during the American Revolutionary War.
Connor Tkachuk is 6'.
Connor Fabiano is 6'.
Connor Franta is 5'9".
Connor Oringderff is 4' 9".
Connor Trinneer is 5' 11".
Connor Stanhope is 5' 10".
Connor McAuley is 5' 6".
Connor McKee is 6' 3".
Connor McShane is 6' 5".
Connor Webb is 5' 8".
Connor Mac is 5' 0".