Disk shows less space than expected

You bought a 512 GB machine, but Windows says the C: drive is 256 GB. Or 240 GB where you expected 256.

There are two different things going on, and it’s worth knowing which one you’re looking at, because one is normal and one is worth fixing:

• A small shortfall is normal. A “120 GB” disk shows up as roughly 118 GB of usable C: drive. Nothing is wrong.
• A large shortfall (roughly half, or a round number like 256 of 512) means part of the disk isn’t being used at all. That space is yours and you can claim it back.

The first step is the same either way: find out how big the disk actually is, as opposed to how much of it Windows has been told to use.

Check the disk’s real capacity

The steps in the video:

1. Open This PC. Windows shows the C: drive, 118 GB in the video. This is the size of the partition, not the size of the disk.
2. Press Win + R to open the Run box.
3. Type ms-settings:disksandvolumes and press Enter. This opens Settings → System → Storage → Disks & volumes.
4. The page lists the disk and the partitions on it, but no sizes.
5. Next to the disk (not one of the volumes indented under it), click Properties.
6. Read Capacity. In the video it’s 120 GB. That’s the real hardware.

So: the disk is 120 GB, and C: is 118 GB. The missing ~2 GB is the hidden EFI and Recovery partitions that every Windows installation has. That’s healthy, so leave it alone.

If instead you find something like a 512 GB disk with a 256 GB C: drive, keep reading.

Tip

Prefer typing? wmic diskdrive get model,size in a Command Prompt prints the raw disk size in bytes. Divide by 1,000,000,000 to compare it with the advertised figure.

Why the space goes missing

When a computer is set up, the installation is copied onto the disk as an image. If that image was built for a smaller disk than the one in front of it, Windows lays down the partitions at the image’s size and simply leaves the rest of the disk unallocated: untouched, unformatted, and invisible in This PC.

The disk is fine. The data is fine. Windows just hasn’t been told it’s allowed to use the rest.

Reclaim it with Disk Management

This is the easiest way and it doesn’t destroy anything.

1. Press Win + R, type diskmgmt.msc, press Enter.
2. Find your disk in the lower panel. If there’s unused space, you’ll see a block labelled Unallocated with a black bar above it.
3. Right-click the Windows (C:) block → Extend Volume.
4. Click through the wizard. It defaults to taking all the available space, which is what you want.

C: grows to fill the disk. No reboot, no data loss, and you can carry on working while it happens.

If Extend Volume is greyed out, skip to When Extend is greyed out below.

Reclaim it with diskpart

Same job from the command line. Use this if you prefer it, or if you’re following instructions from us over the phone.

Open Command Prompt as administrator (right-click Start → Terminal (Admin)), then:

diskpart
list disk
select disk 0
list partition
select partition 3
extend
exit

Read it as: show me the disks → pick the one Windows is on → show me its partitions → pick the C: partition → grow it into the free space.

Two of those numbers are not necessarily 0 and 3:

• select disk 0: list disk prints a table. Match the one whose Size is the real capacity you found earlier. On most laptops there’s only one.
• select partition 3: list partition prints the partitions in order. C: is the big one, usually Primary and by far the largest. It is not partition 1 (that’s the small EFI/System partition).

extend with no arguments takes all the adjacent free space. On success it says:

DiskPart successfully extended the volume.

Type exit to leave diskpart, and check This PC. C: is now the full size.

Caution

diskpart will do exactly what you tell it, including things you didn’t mean. Only ever type the commands above. In particular, clean erases an entire disk without asking, and delete removes partitions and the data on them.

When Extend is greyed out

If Extend Volume is greyed out, or diskpart answers:

There is not enough usable free space on specified disk(s) to extend the
volume.

…then the free space exists, but it isn’t directly after C: on the disk. Almost always there’s a small Recovery partition sitting between them:

[ EFI ] [ Windows (C:) ] [ Recovery ] [ ---- unallocated ---- ]
                          ^^^^^^^^^^
                          in the way

Windows can only grow a partition into space that sits immediately to its right, so the Recovery partition blocks it. Nothing is broken; it’s just a layout problem.

Fixing it means deleting or moving that Recovery partition, and that is genuinely destructive if you pick the wrong one: the partitions either side of it are your Windows installation and your boot files.

Ask us first

Don’t delete partitions to work around this. Deleting the wrong one leaves the machine unbootable, and your data isn’t covered by the warranty. See Our 12-month warranty.

Contact us and we’ll talk you through it, or do it for you. It’s a five-minute job when you know which partition is which.

The trade-off, if you’re wondering: deleting the Recovery partition costs you the built-in “Reset this PC” recovery option. Windows still reinstalls fine from a USB stick, and we can supply one. But it’s your call to make with the facts, not a side effect to discover later.

Still not right?

If the Capacity in the video matches what you paid for but C: still won’t grow, or the numbers don’t match at all, contact us with your order number and a photo of that Properties page. That screen tells us almost everything we need.