Attila Balaton bought an 8GB USB key to create a Windows 10 Recovery Drive only to find out 16GB was required.

Mea culpa: Answer Line was partly to blame, as my former colleague wrote that Microsoft suggests “at least a 4GB USB key.” It’s not his fault, though, as on this support page Microsoft says in order to create a Windows 10 Recovery Drive you will need a, “USB thumbdrive with 4 GB of space or more.” Confusing things further is this page from Microsoft, where the company doesn’t even mention how much space you’ll need. Finally, on its support page for Windows 8 Microsoft says the recovery image the software creates, “…is typically 3 to 6 GB in size.“

However, based on Atilla’s feedback I went in and updated our article. Also in the video that accompanied the above article, we mention that when we tried the process on a laptop in our office it said we needed a 16GB key! This got the staff at PCWorld curious, so we also looked into this further to see if we could nail down a specific size requirement, and also figure out what factors play a role in determining the size of the recovery data.

First, to test what my own system would need I made a recovery drive on my personal PC, which has been running Windows 10 for approximately two years so I figured it would have a lot of system files, or files that needed to be saved. Yet when I went through the process of creating the Recovery drive I was met with the screenshot below.

On my own PCs (both of them) I needed just 8GB of space.

Next I turned to my laptop, which I use only for testing, so it is as minimal of an installation of Windows 10 as you could possibly get. I think the only thing I have installed on that machine is Chrome. Surprisingly Windows told me I needed 8GB for my laptop too!

Therefore, in my experience, with installations of Windows 10 that are both old and new it only required 8GB of storage. Also, when I examined the contents of the Recovery Drive for my personal PC I found it was 6.03GB in size.

Imagine that - only 512MB required!

Back in the office we returned to our 16GB recovery drive. We wondered why it needed to be so large, but then we realized this particular laptop had four user accounts, so we figured maybe it was 3GB per user. That makes sense, right? We decided to ask Microsoft about it, and an “official spokesperson” gave us a statement, which read, “The size of the image varies on a wide variety of factors such as the number of device drivers, OS updates, language packs installed, as well as which version of Windows it is. The recommended size is also rounded up and may show as larger than exactly what is needed.”

Just type Recovery into the Windows 10 search to find the launcher.

That’s great and all, but it didn’t answer our question. When we pressed about how the number of users affects the size of the recovery drive, we received a definitive answer from Microsoft, which was, “The required size of the USB storage is not related to how many user accounts are on the system.”

So there you have it, or at least part of it.

One final ripple: when you start the wizard to create the Recovery Drive it asks you if you want to include System Files as well. When we un-checked this box it said we needed a USB key with a whopping—are you ready for this?—512MB of storage! Do they even make those anymore?

The bottom line is this: A 16GB USB key is only $5 on Amazon, so just get more than you need to be safe. You can also find out the specific requirements of your system by simply running the wizard.

To do that just type Recovery Drive into the Windows search bar and select Create a Recovery Drive from the options. It’ll examine your system and tell you how much space you’ll need before it does anything.