Pittsburgh's Marc-Andre Fleury stuffed the initial shot by Cam Atkinson but Calvert stood all alone at the left post and wristed a shot into the open net to even the Eastern Conference quarterfinals at one game each.
Game 3 is Monday in Columbus.
Jack Johnson tied the game with 6:01 left in regulation for the Blue Jackets. Ryan Johansen also scored the first playoff goal of his career for Columbus. Sergei Bobrovsky overcame a shaky start to finish with 39 saves.
That was something I've been dreaming of, something I've told myself before the third period I was going to do ... It was an amazing feeling. It's hard to describe. I didn't believe it went in at first but when I saw all the reaction and all the fans going crazy and my teammates going crazy, it's just an unbelievable feeling. I didn't know what to do. I didn't know whether to jump or just skate and do a Theo Fleury. I don't think I'm the same caliber player he is so I couldn't do it.
— Flames forward Mikael Backlund on scoring the overtime winner against the Ducks in Gm. 3