Keep in mind that a long movie doesn’t equal an enjoyable movie. Despite the highs of Wonder Woman 1984, one of the biggest criticisms levied against it was its length, which clocks at 2 hours and 30 minutes. Only 17 minutes longer than Black Widow, those extra minutes can still make a world of difference in pacing, which even Warner Bros. seemed to recognize with the long opening of WW84.
On Disney’s official UK webpage for Black Widow, the runtime has been listed as 2 hours and 13 minutes.
This runtime will tie Black Widow as the ninth-longest MCU movie behind all four Avengers movies, Captain America: Civil War, Guardians of the Galaxy Vol. 2, Captain America: The Winter Soldier, Black Panther, and tied with Thor: Ragnarok.