I'm interested in the installation size of Windows 10 when it has been installed on an existing, clean, Windows 7 or Windows 8 installation. By "clean" I mean only a standard non-OEM OS and critical drivers, and updates.

For example:

  1. A computer is installed with a typical Windows 7 Ultimate x64 OS
  2. Critical updates are applied to the point that the Windows 10 Upgrade tool is installed
  3. Disk cleanup is executed to recover as much space as possible
  4. The upgrade tool is used to perform the OS upgrade
  5. After the upgrade is complete Disk Cleanup is again performed to recover space

How many GB would this occupy? Would there be a significant difference if upgrading from Windows 7 vs. Windows 8?


Microsoft says 20 GB for 64-bit OS.

I did a clean install, 12GB. Then added office, 16GB.

Then after a couple of days of windows update 50GB + 10GB in Recycle. 31 Gig in C:\Windows, 5 gig page and hibernate files.

And it grows substantially over time. 120Gig minimum.

This is for a clean install onto a new disk, keeping nothing. You are braver than I am to try an upgrade. My previous Win 7 install had suffered from windows rot (degeneration of the registry over the years) so needed blasting anyway.

(I use a Gargoyle router to throttle the windows update downloads from killing the internet for everyone.)


Depending on the size of the drive, after Disk Cleanup, and the size and number of System Restore Points, you can expect a footprint of from around 22gig to as large as 35 gig. This is assuming the Documents folder and Pictures folder do not hold much data.

  • 9
    Neither of those documents would have any data given the clean installation aspect of this question. Microsoft's own information indicates that a clean installation of Windows only takes 16GB if it's a 32-bit installation and 20GB if its a 64-bit installation. – Ramhound Oct 16 '15 at 14:54

Today (2018-03-30) I did a clean* install of Windows 10 Pro with 23 GB.

* For me, this includes deleting all unnecessary pre-installed programs (for instance games, OneDrive, Weather, News, etc.), getting the newest updates, and running Window's Disk Clean-Up tool afterwards.


Windows 8.1 install with updates 40 GB

There are programs like Win Reducer and NT lite to remove unwanted bloat ware.

But you should know what the components you are removing are as you could remove critical system files.

Alternatively, change permissions of the entire C: to give you full access to delete files through the "Properties" "Security" "Advanced" settings Change principle, etc.

Then you can do search for things like

Built in apps like Weather News etc.

Just delete them.

Fonts and Languages that are not used can be deleted, as well.

Most other stuff in the WinSXS folder are drivers, and most of them are just incase your system has those devices.

It just covers more computers when you buy the software.

If you know what you are doing most of that can go.

Then there are things like Pagefile.sys and swapfile.sys which is the hybernate files

Turning off Hybernate will remove this.

In a Command Prompt as Admin, run the following:

"powercfg.exe /hibernate off"

Then there are TEMP folders in Windows and the appdata folder under "Users" these are mostly reminants of installation packages.

They can also go.

Just the temp and page files removed are around 3-5gb freed up.

For more on this: https://www.youtube.com/watch?v=iMX5wi7Vz0Q


Here they point out, that Compact OS can reduce the footprint from 12,3GB to 10,3GB.

So it is reasonable to assume 12,3GB to be the footprint of a windows 10 install.

  • Seems like those numbers are only in the archived version of the page. Live one reports almost double figures. Unsure if just due to random updates of a "non-clean" installation, or increased requirements on the part of newest W10 versions. – mirh Jan 29 '18 at 20:36

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.