Question How to calculate the precise partition size for a desired displayed size in Windows?

[Pimpom]

When I create partitions on a new disk, I like to have the sizes show up as nice round figures in Windows - like 50.0 GB, 400 GB and so on. When I specify the desired size, they show up as slightly less - like 49.9GB, 399GB, etc. Please note that this is not a matter of decimal vs binary units. E.g., 204800 MB show up as 199 GB.

I suppose that this is caused by partition overheads such as the AU table stealing a small amount of space. I compensate for this by adding a few MBs during partitioning. I've been doing this for a long time but I usually arrive at the amount to add by trial and error. Is there a way to calculate the precise amount of space that needs to be added to get the desired displayed size?

 

[TerryLaze]

Please note that this is not a matter of decimal vs binary units. E.g., 204800 MB show up as 199 GB.

It should though because it's the only explanation, it's the difference between gigabit and gigabyte.
https://microsoft.fandom.com/wiki/Gigabyte

 

[Ralston18]

Two thoughts:

1) You easily obtain a great deal of information about disks and disk configuration via Powershell (e.g., Get-Partition).

FYI as an example:

https://learn.microsoft.com/en-us/powershell/module/storage/get-partition?view=windowsserver2022-ps

Note all of the other disk related "Get" 's in the left side column.

You can google for other similar links, tutorials, examples, scripts, etc..

2) Why even make the effort? My recommendation is to just allow Windows to "be Windows" and not attempt to out guess or second guess Windows with a lot of tweaking or gaming the OS to show a "round number" via Disk Manager, etc..

Probably not worth the time and effort especially with today's disks (SSDs) and disk capacities. And just adds opportunities for mistakes, errors, and issues.

If really concerned about showing rounded partition sizes I suggest just compromising: Let Windows manage the reported partition sizes and you use Powershell Get's (or PS scripts with Gets) to monitor the disk partition sizes to whatever degree of accuracy you can and wish to round to.

Then output to screen or printer via a desktop shortcut icon.

Run Get-Partition (as admin) per the link to get a sense of it all.

But to be fully workable with respect to your requirements you may need a script.

Note: you did get me interested in something else.

https://devblogs.microsoft.com/scripting/powertip-use-powershell-to-round-to-specific-decimal-place/

Have not worked that (full disclosure) but added to "my list".

 

[USAFRet]

like 50.0 GB, 400 GB and so on. When I specify the desired size, they show up as slightly less - like 49.9GB, 399GB

1. Rounding errors in the reporting.
2. Gigabyte vs gibibyte. (Base 2 vs Base 10)

 

[geofelt]

What is your purpose in such micro partitioning?

 

[SkyNetRising]

When I create partitions on a new disk, I like to have the sizes show up as nice round figures in Windows - like 50.0 GB, 400 GB and so on. When I specify the desired size, they show up as slightly less - like 49.9GB, 399GB, etc.

Is it some form of OCD ?
Generally you should not care about such rounding errors.
This changes nothing and has no impact on anything.

 

[TerryLaze]

Is it some form of OCD ?
Generally you should not care about such rounding errors.
This changes nothing and has no impact on anything.

You don't need to have OCD for this to be annoying, I find it annoying as well, just not enough to do anything about it.

 

[slightnitpick]

I have OCD, but don't need this kind of symmetry. Try this calculator to see if it works: https://partition.toolpie.com/

And here's a Stack Overflow answer: https://superuser.com/questions/217...tion-to-appear-as-a-standard-number-e-g-100gb
(You'll probably have to adjust this answer for whatever your allocation unit size is.)

 

[fzabkar]

sgdisk can do it:

https://linux.die.net/man/8/sgdisk