Wrong Capacity After Formatting to FAT32: Restore Full Size
Warning: formatting erases everything on the selected volume. Back up any files you need first, and double-check the drive letter before you click Start. Formatting the wrong drive will erase the wrong files.
A card that shows less capacity after formatting is alarming, but it is often a partition problem, not a shrinking card. Formatting only rewrites the file system inside a partition. It does not change the partition size. If the partition was created smaller than the card, or if part of the card is left unallocated, Windows will report only the partition size, and the rest will look missing. A second possibility is simpler: advertised capacity and Windows capacity are measured differently, so a 128GB card never shows as a full 128GB in Windows. A third possibility is serious: a counterfeit card that reports more space than it physically has.
Fix in order
- Check the real numbers first. Open Disk Management with Windows + X and find the card by its total disk size. Note the size of each partition and any unallocated space. If the disk total looks right but one partition is small, the missing space is almost certainly unallocated space, not lost hardware.
- Do not panic about a small shortfall. Drive makers count a gigabyte as 1,000,000,000 bytes, while Windows counts it as 1,073,741,824 bytes. That alone makes a nominally 128GB card show around 119GB. File system overhead takes a little more. A shortfall of roughly that scale is normal and is not a fault to fix.
- Reclaim unallocated space. If Disk Management shows unallocated space beside a small partition, you can extend the partition into it, or delete the small volume and create a new volume using the full space. Only delete a volume if you have backed up its contents, because deletion erases it. Then format the new, full-size volume to FAT32 with guiformat, checking the drive letter first.
- Restore full capacity from scratch. If the layout is messy, with several small partitions or a leftover partition from another device, the cleanest route is: in Disk Management, delete the volumes on that card only, create one new simple volume using all available space, then format it to FAT32. Verify the disk size at every step, so you do not delete a volume on a different drive.
- Check for a second partition. Some cards arrive with a small hidden or recovery partition. That partition takes space and can confuse capacity readings. Do not delete a partition you do not understand on a drive you still need, but on a blank card you intend to reuse, a single full-size partition is usually what you want.
- Test for a fake card if the numbers do not add up. If a card claims 512GB but consistently fails after writing far less, or files vanish after you copy them, run a write-and-verify test with a free tool such as h2testw. It writes test data across the card and verifies it, which takes a long time on a large card. Run it only on an empty card, because it fills the card with test files, and delete those test files afterwards.
Why cluster size is not the usual culprit
Cluster size affects wasted space, not reported capacity in the way expected. A large cluster size means small files waste more space inside their clusters, so a card full of tiny files will hold fewer of them. It does not normally make a 128GB card report as 32GB. If your card reports a smaller size, look at partitions and unallocated space first, then counterfeit-card signs. Changing cluster size alone will not restore that space.
The 4GB single-file limit also does not reduce total capacity. If you cannot copy a large video, the problem is the file size, not missing capacity: split the file, or use a file system the device supports.
| What Disk Management shows | Likely cause | Fix |
|---|---|---|
| Disk total looks right, partition is small | Unallocated space beside it | Extend or recreate one full-size volume |
| Disk total itself is far too small | Wrong card, damaged card, or fake card | Test in another reader; run a verify test |
| Several small partitions | Leftover layout from another device | Delete card volumes only; create one volume |
| Only a few GB short | Advertised vs Windows counting | No fix needed; this is normal |
Fake and counterfeit card warning signs
A counterfeit card is programmed to report a larger capacity than it has. Early use looks normal, because files are written to real space first. Once writing passes that real capacity, new files overwrite old ones or vanish. Signs include a price far below normal, an unknown seller, and files that become unreadable once the card is nearly full. A write-and-verify test checks what can be read back, not what the card claims.
If a test proves the card is fake, do not keep using it for important files. No format or partition trick creates physical storage that is not there. Keep proof of purchase, contact the seller, and replace the card from a trusted seller.
What NOT to do
- Do not delete volumes on a disk you have not identified by size. Disk Management lists every drive, and deleting the wrong one erases the wrong data.
- Do not run a write-and-verify test on a card with files you need. The test fills the card, so back up first or use an empty card.
- Do not assume a format will fix a fake card. Formatting rewrites the file system; it does not add storage.
- Do not keep copying files onto a card that loses data after a certain point. Stop, test it, and replace it if it fails.
If this did not work
If Disk Management shows the full disk size but no partition tool can create a full-size volume, try another reader and another PC. A faulty reader can misreport size, and a second reader quickly separates a reader problem from a card problem. If the card shows a far smaller total on every reader and PC, and a verify test fails, treat it as damaged or counterfeit and replace it.
If the card shows the right size after you recreate the volume but your device still reports less, check the device manual for a maximum supported capacity. Some older devices only address part of a large card. In that case the PC is correct and the device is the limit, and a smaller card that the device fully supports is the practical answer.
This site is unofficial and unaffiliated with RidgeCrop and Microsoft. Guiformat is Windows-only and formats an existing partition; it does not create or resize partitions, so the Disk Management step above comes first when space is unallocated.
FAQ
Why does my 64GB card show about 59GB? That is mostly the difference between how makers count gigabytes and how Windows counts them, plus file system overhead. It is normal, not missing space.
Will reformatting to FAT32 restore the missing space? Only if the partition itself was too small and you recreate a full-size partition first. Reformatting the same small partition will give you the same small size again.
How long does a write-and-verify test take? A long time on a large card, because it writes and then reads back the whole capacity. Start it when you do not need the card, and leave the reader undisturbed.
Is my card fake if it shows less than advertised? Not necessarily. A small shortfall is normal. A card is suspect when it claims a large size but fails a full verify test, or loses files once it passes a much smaller amount of written data.