Borderlands 3 Inventory Guide – Where to Buy an SDU & Lost Loot

Capitalism has finally hit us where it truly hurts: our backpacks.

Your Borderlands 3 inventory is your lifeline. In a game all about guns, grenades, and guns that turn into grenades, you want to carry as much stuff as possible. Sadly, your inventory limit is… pretty limited. At least it is at first! Push through the story and you will quickly unlock the ability to upgrade your inventory. Much like in the previous games, you just need to buy a SDU. This will expand inventory space and just generally let you pick more stuff up. There are a few other wrinkles, however, so let’s take a look in this Borderlands 3 inventory guide!

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Your journey through Borderlands 3 begins on Pandora — the same planet where the first two games took place. However, if you stick with the story missions, it won’t be long before you leave that horrible rock in favor of the stars. There are several new worlds to explore; you unlock them as you progress through the campaign. But first you’re given access to yet another new and improved version of Sanctuary. This mobile base has all the comforts of home! That includes your bank vault (for extra storage), slot machines (for spending excess cash), and Marcus Munitions.

You can’t miss Marcus. Shortly after taking off in Sanctuary, you will be forced to help save his shop from a fire. As a reward, he’ll give you access to his store of SDUs. These are various types of inventory upgrades in Borderlands 3. If you’ve played Borderlands before, you probably already know how they work. But here’s the short version: every SDU will upgrade your inventory by a certain number. This applies to grenades, ammo for certain kinds of guns, and your Borderlands 3 backpack itself.

We absolutely recommend buying as many backpack SDUs as possible. Inventory management in Borderlands 3 is, simply put, not great. There’s no way to break down your guns, grenades, or shields in the field. You can only either drop them or sell them at specific vending machines. And those vendors are surprisingly few and far between. Increase your inventory limit to make Borderlands 3 a much smoother experience.

There is a catch, however. Every SDU you purchase of a given category will increase the cost of the next SDU. Yet the benefit doesn’t increase; every Backpack SDU increases your inventory space by three slots, no matter how expensive it is. Odds are you won’t be able to max out your inventory space in Borderlands 3 for quite some time.

Borderlands 3 Inventory Upgrade

Lost Loot – Borderlands 3 Inventory Guide

There is a useful workaround, though! Marcus will also sell you a Lost Loot SDU at the same shop. This convenient mechanic kinda-sorta increases your inventory space by one slot further for each SDU. Sanctuary is also home to a device called the Lost Loot machine, located at the rear of the ship. This is where you can find certain loot you fail to pick up in the field when you return home.

Lost loot is limited to Rare (blue) quality gear, however. Grey and green gear will just disappear if you leave it behind. And the Lost Loot Machine has a pretty limited inventory itself — even with upgrades. You will need to empty it out periodically. Luckily, it’s located right next to your personal quarters and the bank vault therein. And wouldn’t you know it? Marcus will also sell you a bank SDU. It’s the circle of inventory management, baby!

Of course, you can also just sell your gear periodically. We recommend dumping any grey and green quality gear with a lower item score than whatever you’re carrying. You can even mark them as junk to sell in bulk. However, since you have to mark them manually, it’s not that much more convenient than selling them piece by piece. It’s a good source of cash, though… which you can then pump into more SDUs in Borderlands 3. Put it towards a Backpack SDU first. Then, if you don’t have enough for that, grab the Lost Loot SDU next. The lower-leveled inventory upgrade should remain a cheaper (if slightly less convenient) option).

And there you have it! That’s all you should need to know about how to upgrade your inventory in Borderlands 3. Thanks for taking the time to figure it out. Now get out there and grab an SDU, Vault Hunter! You’re going to need it…