According to Jonathan Morin, the Creative Director at Ubisoft Montreal, Watch Dogs should clock in at around about 35 to 40 hours of story.
Jonathan Morin, the Creative Director at Ubisoft Montreal, has responded to fan speculation via Twitter to state that Watch Dogs should hit around about 35-40 hours of game time to reach the ‘end’, providing the player free roams a bit. However, he goes on to say that “doing everything” in the game will hit you closer to 100 hours of game time.
@vytla102 I would say the average player which does free roam a bit tend to reach the end within 35-40h. But doing everything is close 100h.
— Jonathan Morin (@Design_Cave) March 15, 2014
From this, we can presume that the main story will be approximately 25 to 30 hours long, with the ‘free roam’ likely to be several hours. The additional content is likely to be a series of side missions, achievements and collectables.