Starfield’s story is approximately 30 to 40 hours long.
Game director Todd Howard has revealed the Starfield story length. He explained that it is much longer than Skyrim and Fallout 4.

Starfield was featured extensively at the Xbox & Bethesda Games Showcase last Sunday, and more details are now being shared, with a release early next year. It’s already obvious that it’s a massive game, but how long exactly have you been working on the story?
Todd Howard provided more clarity on this in a conversation with IGN. The game director notes that the game is richly filled with all kinds of missions, making Starfield about a fifth longer than, for example, Skyrim and Fallout 4.
Will Starfield be released for PS5 and PS4 platforms?
To give a more specific time, Howard estimates the total duration of the story at 30 to 40 hours. The number of hours is somewhat dependent on how many side quests the player undertakes, so in the case of ‘doing everything’ in the game the time tends to be 40 hours.
Game director Todd Howard has revealed the Starfield story time. He explained that it is much longer than Skyrim and Fallout 4.