This page will provide you with the necessary steps to increasing your Backpack Capacity in Tiny Tina’s Wonderlands.
Where to Upgrade Your Storage Capacity in Tiny Tina’s Wonderlands
Like all Borderlands Games you’ll be finding lots of loot throughout your adventure, so you’ll need to work on increasing your backpack capacity as soon as possible to avoid leaving good loot on the floor or clogging up the Lost Loot with pointless weapons. Your first step to improving your backpack is to gain access to the main hub of Tiny Tina’s Wonderland, Brighthoof.
In order to do this you’ll need progress through the Main Story until you’re forced to take a portal back to Brighthoof, then after some dialogue you’ll be told to visit the Blacksmith who can be found working in the northeast corner of the city. Speak with the Blacksmith to get an introduction on increasing your Bank, Ammo, and Backpack Capacity, then approach and interact with the machine to the left of her to be given a variety of Storage Deck Upgrades.
However, the fee will increase when you upgrade a certain SDU multiple times, so for the early portion of the game you’ll want to work on increasing your Backpack as much as possible, as you’ll be picking up all the loot you can find, then work on increasing the capacity for a weapon you use the majority of the time.