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How to increase inventory space in Borderlands 3

Borderlands 3 is a game all about loot. Here’s how you increase how much of the stuff you can carry.



Borderlands backpack

Borderlands 3 is a game all about loot. Here’s how you increase how much of the stuff you can carry.

Borderlands 3 follows some pretty standard RPG progression mechanics. That seems commonplace now, with the likes of Destiny and The Division, but when Gearbox first mashed up RPG and FPS, back in 2007? It was a rare treat.

First, you’ll pick your character class. Then as you level up and fill out your skill trees, you’re able to customise your character with class mods.

As the game progresses, you’ll increase the number of weapon slots from two to four. But Borderlands 3 is a game with billions of guns. Even when you’ve upgraded to four weapon slots, you might still be carrying around more than four. Some of those will be to sell, in true looty-shooty fashion, while others will be spares/swap weapons for specific scenarios.

To carry more guns (and other items, like class mods and shields) you’re going to need to increase your inventory size. This is done via storage deck upgrades, or SDUs.


What is an SDU?

An SDU is a permanent upgrade that, once applied, will allow you to carry more. Storage deck upgrades also stack sequentially. That means you can apply the first backpack SDU, for example, and it will increase your inventory carry slots by a small amount. Once you’ve got the first backpack SDU, then the next one you apply will increase your carry slots by even more.

There is a limit to how many storage deck upgrades you can apply for any given inventory type, but the idea is that as you progress through the game, level up your character, and find more loot, you’ll be able to increase your carry space to match.

What SDU types are there?

In Borderlands 3, as in the previous games, there are two main types of storage deck upgrades: backpack SDU, and ammo SDU.

The backpack SDU, as described above, increased your number of inventory slots. This is how much stuff you can carry, in terms of discrete items that don’t stack in a single inventory space (like guns and shields, but not ammunition).

Ammo storage deck upgrades come in different flavours, and increase your overall carry capacity for each specific ammo type. Pistol, revolver, shotgun, SMG, assault rifle, rocket launcher, grenade – each gun takes its own distinct type of ammo, and as a result, each ammo SDU can be increased independently. Like the backup SDU, they also grow cumulatively larger with each subsequent upgrade. This is another way to customise your character based on your playstyle and weapon preferences – it makes sense to focus on upgrading capacity for your favourite/most used type of weapon, and you might need to prioritise in the early game when resources are more scarce.


How do you increase your inventory?

To increase your inventory, you need to get storage deck upgrades. And like other progressions in Borderlands 3, you need to reach a certain point in the story – when you reach Sanctuary 3, the hub town spaceship – early in the story. Unlike other progression types, however, which are just gated behind main story missions, you need to purchase storage deck upgrades from a shop. With money.

Specifically, that shop is Marcus’ Munitions on Sanctuary 3. Instead of visiting the vending machines – that allow you to buy weapons or ammunition – you need to visit the big counter that Marcus is standing behind. From there, you can purchase storage deck upgrades. Those first, lower-level upgrades will seem relatively cheap, but as they move up through the capacity levels, they’ll become more expensive, and maxing out everything will be rather expensive.

We would, therefore, recommend prioritising based on your favourite gun types, and going for the backpack SDU early – the more stuff you can carry, the more stuff you can sell. The more stuff you can sell, the more storage deck upgrades you can buy.

You know it makes sense.

More Borderlands 3 from Thumbsticks

Header image: Borderlands messenger bag by Numbskull


Tom is an itinerant freelance technology writer who found a home as an Editor with Thumbsticks. Powered by coffee, RPGs, and local co-op.


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