On this page of our guide you will find out how long it can take you to complete Doom Eternal. Of course, please note that this is not a fixed value and may change depending on the way the game is played.
During the QuakeCon 2019 event, Marty Stratton from id Software has revealed that it will take more time to complete Doom Eternal than in the case of the previous parts of the series. This means that it should take you around 18 to 20 hours to finish the main story campaign and discover all secrets in the game.
The time given above refers to the story campaign implemented in the game. Apart from that, the game will also offer a multiplayer mode, which can significantly increase the number of gameplay hours.