Emergency · unstable memory card
Memory card shows the wrong capacity
What should I do when a memory card reports the wrong size?
Short answer
First test it in one known-good reader: a faulty reader, damaged partition data, a failing controller or counterfeit flash can each distort the size. If the correct capacity appears there, a read-only scan makes sense. If the card itself still reports the wrong size, stop scanning, because software cannot read blocks it never receives.
The situation
A known card enumerates with a much smaller, larger, or fluctuating capacity.
Capacity is reported by the card controller, long before any file system is involved. A wrong figure therefore points at the hardware path first: the reader, the adapter, the controller or the flash behind it, and only then at damaged partition data.
01 / Diagnose
Work out what actually disappeared
Four causes produce the same symptom. A tired reader or a loose adapter can enumerate the card incorrectly. Damaged partition metadata can make a full card look tiny. A failing controller reports whatever it can still manage, often a few megabytes or a fluctuating number. And counterfeit flash is built to report a size it never had.
Reader faults, controller failure, counterfeit flash, or damaged partition metadata can all distort capacity.
Check the last known path, trash and backups without writing to the original device.
02 / Protect the source
Preserve the best recovery chance
- 1
Try the card in one reader you know to be good, connected directly to the computer, and read the capacity there.
- 2
Compare three figures: the size printed on the card, the size the disk utility shows for the physical device, and the size of the volume.
- 3
If the device now shows its true capacity, image it once or scan it read-only before doing anything else with it.
- 4
If the wrong figure follows the card from reader to reader, stop scanning and get a quote from a data recovery lab.
Do not accept the offer to initialise, partition or format the card so that it shows the right size again. That creates a new structure over data whose true extent is still unknown, and it does not repair a controller or replace missing flash.
03 / Choose the method
Match the tool to the source
For stable, readable exFAT, NTFS and FAT16/FAT32 or uncompressed IMG, DD, RAW and BIN images.
Unconfirmed exports are marked .UNVERIFIED.
Software can only read blocks the operating system receives from the device, so a card that never presents its real size is outside the reach of File Recovery Hero and of any comparable tool. That case belongs to a lab with chip-level equipment.
04 / Verify
Check the recovered content, not just its name
The card is usable again for reading when the physical device reports its printed capacity in two different readers and the figure stays stable during a long sequential read. Recovered files then have to open completely, since a wrong geometry tends to produce plausible-looking but broken exports.
Keep the source until two verified copies exist. One working preview is not enough.
Sources and technical references
FAQ
Questions about this recovery case
Can unstable memory card be recovered in this situation?+
Capacity is reported by the card controller, long before any file system is involved. A wrong figure therefore points at the hardware path first: the reader, the adapter, the controller or the flash behind it, and only then at damaged partition data. The result still depends on what remains readable on the source.
What should I avoid before scanning?+
Do not accept the offer to initialise, partition or format the card so that it shows the right size again.
Does scanning write to my memory card?+
Your memory card is only read. Nothing is saved to it.
How do I know whether the result is complete?+
The card is usable again for reading when the physical device reports its printed capacity in two different readers and the figure stays stable during a long sequential read.