What can I do to make the C drive 250 GB when installing Windows?

Question

I want to install Windows 11

How do I enter the storage amount of drive C in the partitioning section of Windows 11 installation so that it shows me exactly 250 gigabytes.

For example, how do I enter 150 or ‌250 so that it shows exactly the same amount after installing Windows 11 in Thic PC under drive C?

I don't want 250 gigabytes to show 249

Answer 1

Windows setup uses binary (GiB) units, while File Explorer shows decimal (GB) units.

• 1 GiB = 1,073,741,824 bytes
• 1 GB = 1,000,000,000 bytes

If you want it to show 250 GB in File Explorer, you need to allocate about 268 GiB. During installation, when it asks for partition size (in MB), enter 256,000 MB (≈ 250 GB shown later in File Explorer). That's because:

• 256,000 MB × 1,048,576 bytes ≈ 268,435,456,000 bytes
• 268,435,456,000 bytes ÷ 1,000,000,000 ≈ 250 GB

So after installation, File Explorer will show very close to 250 GB for drive C.

Note that after installation, Windows reserves a few hundred MB for:

• The System Reserved partition (100–550 MB)
• Recovery partition (500–1000 MB)
• File system overhead

So even if you specify the “perfect” size, you might see minor deviations...

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hth

Marcin