Towards the start of Borderlands 3, your inventory is quite small in size. It will soon fill up as you pick up weapons, shields and grenades after killing enemies and searching containers.
Once you have left the starting area, you’ll begin to be able to upgrade your inventory, by purchasing new slots. You’ll also have access to a bank, where you can also store items that you don’t need at all times.
Below, we’ll show you how to upgrade your inventory and backpack size in-game. For more Borderlands 3 Guides & Best-of content for PS4, PC and Xbox One, make sure to check out our dedicated area here!
Increasing Inventory Size
You can increase your inventory size once you reach Sanctuary. On-board, you will find Marcus in his store, Marcus Munitions. There is a small quest you will have to complete before he’ll let you access his store.

Marcus sells items called SDU’s, which means Storage Deck Upgrades. These items where also available in Borderlands 2, but where sold by Crazy Earl for Eridium. Whereas Marcus sells them for cash.

SDU’s increase ammo capacity, bank slots, grenade capacity and backpack capacity, which is what we need. The first tier will cost $1000 in-game cash, $3000 for the second tier and so on.