Question Installing Windows 11: Getting exact size for Windows C:\ partition

[Dave3000]

I right now have a 149 GB C:\ partition on my 2 TB SSD, but I wanted to create an exact sized 150 GB for C:\ along with the normal sizes for the other partitions that the Windows 11 installer creates during the installation. I know that I can just run a 3rd party partition manager to adjust the sizes of the partitions after the Windows installation but I prefer doing it during the Windows installation and then creating the remaining allocated space for my data which consist of games, user library folders, and drivers. I did find a website that tells you the size partition you need to set during the Windows 10 installation to get a specific size you want for the C:\ partition if including the other partitions that Windows 10 creates but nothing for Windows 11 (23H2). This is the site I'm referring to: https://windowspro.eu/windows-partition-calculator-install/ Here's how I want it set: 100MB ESP -> 16MB Reserved -> 150GB C: Windows -> 768MB Recovery -> 1.67 TB D: Data. I want it to display exactly 150GB for C:\ in "This PC" section in Windows 11. Is there any easy way to accomplish this other than through trial and error to get that exact 150GB for C:\ partition? When I mentioned GB and TB, I really mean GiB and TiB respectively.

 

[Dave3000]

I now have it set as about 125 GB (not GiB) partition for Windows 11 C:\ and about 1875 GB partition for Games D:\ on my 2TB NVMe SSD. However, before this I did find a way to get exactly 150 GiB (153,600 MiB) for C:\ during the Windows 11 installation, at least it showed the exact number in the Windows Disk Management utility and Diskpart for C:\, but it showed only 149 GiB for C:\ in explorer. I had to also add the size of other partitions that Windows creates during the installation plus 1 MiB in my calculation. So, 100 + 16 + 153600 + 768 + 1 = 154485 for the number I must enter in the box to get an exact 150 GiB C:\ to show in the Window Disk Management Utility.

 

[zir_blazer]

I would assume that you can't get a rounded 150 GiB because the PARTITION is 150 GiB, but the File System whose metadata is inside the Partition also takes space. So Properties may likely tell you the usable size after File System overhead, not Partition.

 

[Dave3000]

I also ran diskpart and assigned the letter R to the 768 GiB recovery partition that Windows installation created. Even though it shows 768 GiB in diskpart and the Disk Management utility, it shows 767 GiB for drive R under explorer. Also I ran diskpart again and assigned the letter X to the 100 MiB EFI partition that Windows installation created. Even though it shows 100 MiB in diskpart and the Disk Management utility, it shows 96 MiB for drive X under explorer.