Have you connected a flash drive or memory card to your smartphone on Android, but are not sure that the volume indicated on the package corresponds to reality? Or did the free space suddenly halve after formatting? The problem of counterfeit drives is still relevant - according to research Counterpoint Researchup to 15% of flash drives on the market have an underestimated real capacity. And file system errors (for example, after incorrect extraction) can “eat up” gigabytes of space for no apparent reason.

In this article we will analyze 5 ways to check the capacity of a flash drive on Android —from built-in tools to specialized applications. You will learn how to distinguish an original card SanDisk Ultra from a fake, why a smartphone shows less memory than expected, and what to do if the drive is detected as “damaged”. We will pay special attention hidden sectionsthat some manufacturers create (for example, Samsung for functions Secure Folder), and we will explain how to take them into account in the calculations.

Important: if you use a flash drive to record video to 4K or work with applications (function Adoptable Storage), checking the volume should include a test for recording speed - we will also talk about this below.

1. Standard method: through Android "Settings"

The fastest method is to use the built-in system tools. It is suitable for checking both USB drives (via OTG adapter) and microSDcards. The instructions are valid for all versions of Android, starting with 6.0 Marshmallow:

  1. Connect the flash drive to your smartphone. For microSD use the slot (if there is one), for USB — OTG adapter (check compatibility in the device characteristics).

  2. Open Settings → Storage (on some firmware the path may differ: Settings → Memory and storage → Additional settings).

  3. In the section "Portable storage" or "SD card" you will see:

    • 📊 Total volume (for example, 128 GB)
    • 📥 Used space (including system files)
    • 📤 Free space

⚠️ Attention: If after connecting the flash drive nothing appears in this section, check:

  • 🔌 Correct connection (try another OTG adapter or slot)
  • 🛠️ File system format: Android does not support NTFS"out of the box" (you need an application like Paragon NTFS)
  • 🔄 Availability of a connection notification in the curtain (sometimes you need to allow access)
💡

If The flash drive is detected, but shows the volume 0 bytes or asks to format it - don’t agree right away! Try connecting it to the PC first: perhaps the problem is in the file system, but the data can still be recovered.

2. Through "Explorer" or "Google Files"

Built-in file managers (for example Google Files or standard Explorer from the manufacturer) also display information about connected drives. This method is convenient if you need to quickly check several flash drives in a row:

  1. Open the application Files (or My file on Samsung, File Manager on Xiaomi etc.).

  2. In the side menu, select section "Storage" or "Devices".

  3. Find your flash drive in the list (usually it is labeled as USB drive or model name microSDClick on). three dots next to the name and select "Properties" or "Information".

Here you will see:

  • 📏 Full volume (may differ slightly from stated due to formatting)
  • 📁 File system type (FAT32, exFAT, ext4)
  • 🔒 Protection status (if the flash drive is write-locked)

🔍 Why is the volume less than stated? Manufacturers indicate the capacity in decimal gigabytes (1 GB = 1,000,000,000 bytes), and Android shows binary gigabytes (1 GiB = 1,073,741,824 bytes) The difference for 128 GB may. reach 7-10 GB!

📊 Which file manager do you use on Android?
Google Files
Standard from the manufacturer
Solid Explorer
FX File Explorer
Other

3. Specialized applications for testing

If you suspect that the flash drive is a fake (for example, purchased on an unknown marketplace at too low a price), standard methods may not show the real volume. In this case, applications that record test data on the drive and check its actual capacity will help.

The best tools for this task:

Application Functions ROOT required? Link (Google Play)
SD Insight Shows the real manufacturer and model of the memory chip, detects fakes No ✅ Available
FlashBench Tests read/write speed and checks the actual volume No ✅ Available
FakeFlashTest Writes files over the entire volume, identifies "broken" sectors No ⚠️ Removed from Play (download APK from the official website)
A1 SD Bench Full performance test + volume check No ✅ Available

📌 How to use FakeFlashTest:

  1. Select the flash drive in the list of drives.

  2. Click "Select All" and run the test.

  3. The application will start writing files to all sectors If the process. will abort with an error "Cannot write to disk" —your flash drive is fake, and its real capacity is less than declared.

What to do if the application does not see the flash drive?

1. Check that the drive is formatted in FAT32 or exFAT (Android does not support NTFS without additional drivers).

2. Connect the flash drive via another OTG adapter —some cheap adapters do not provide enough power for power drive.

3. Reboot your smartphone: sometimes the system does not immediately recognize external devices.

⚠️ Attention: Tests with data recording (FakeFlashTest, FlashBench) will delete all information on a flash drive! Before checking, copy important files to another drive.

4. Check via PC (for accurate diagnostics)

If you cannot get accurate data on your smartphone, connect the flash drive to the computer. This will help:

  • 🔍 See real controller model (through ChipGenius or Flash Drive Information Extractor)
  • 📊 Check read/write speed (apps CrystalDiskMark, H2testw)
  • 🛠️ Recover data if the flash drive is detected as RAW

Instructions for Windows:

  1. Connect the flash drive via a card reader or OTG adapter + cable USB-TypeC.

  2. Open Disk Management (click Win + X → select the appropriate item).

  3. Find your drive in the list:

    • 📌 Size (should. match the declared one)
    • 📌 File system (if RAW —the flash drive is damaged)
    • 📌 Status (should be "Good")

  • For a deep check, download H2testw:

    1. Select the flash drive in the list

    2. Click "Write + Verify"
    

    3. Wait for completion (may take several hours for large volumes)
    

    4. If the test shows errors, the drive is fake or damaged

    • Critical! If H2testw shows that the actual capacity of the flash drive is 4 GB, and it is written on the case 128 GB - this is 100% fake. Such drives can save files only up to their real limit, and then the data begins to be overwritten on top of the old ones, which leads to their irretrievable loss.

    Disconnect the flash drive from the smartphone|Use the original cable/card reader|Make a backup copy of the data|Close all apps using the drive|Check with an antivirus for malware-->

    5. ADB commands for advanced users

    If you have experience with Android Debug Bridge (ADB), you can get detailed information about the flash drive via the command line. This method is useful if:

    • 🔧 You need to know serial number drive
    • 📊 Check partitioning (for example, for Adoptable Storage)
    • 🛠️ Diagnose mounting errors

    Instructions:

    1. Enable USB Debugging in the developer settings (Settings → About phone → Build number (press 7 times) → Return to Settings → System → For Developers).

    2. Connect your smartphone to the PC and open the terminal (or PowerShell in Windows).

    3. Enter the commands:

      adb shell

      sm list-disks

      This command will show all connected drives, including the flash drive. Pay attention to the identifier like disk:179,64.

    4. To find out details about a specific drive, run:

      sm partition disk:179,64

      Replace 179,64 with your identifier.

    📌 Example output:

    Disk: 179,64

    Info: /dev/block/vold/disk/179:64
    

    Size: 119.2 GB
    

    Erase Size: 512 bytes
    

    Logical Sector Size: 512 bytes
    

    State: Idle

    ⚠️ Attention: Commands ADB may change the partition structure if used incorrectly, Not. do sm partition with the parameters if you do not understand their purpose!

    💡

    If the flash drive is detected in ADB, but is not visible in the standard Android interface, the problem is in the file system. Try formatting it. via PC, and then connect again. FAT32 via PC, and then connect again.

    6. How to recognize a fake flash drive: 5 signs

    Fake drives are often disguised as brands SanDisk, Samsung or KingstonHere's how. identify them before purchase and after:

    Signs of counterfeit:

    • 💰 The price is too low (for example, 256 GB for 500 rubles - a clear sign of fraud)
    • 📦 Poor quality packaging (blurred font, lack of hologram, typos in the model name)
    • 🔠 The serial number is not checked on the official website of the manufacturer
    • 📉 Write speed below 5 MB/s (even for budget models this is not normal)
    • 🔄 After formatting volume is "restored" (fake flash drives often reset the counter after cleaning)

    🔍 How to check the serial number:

    1. Find the number on the flash drive case (usually starts with letters, for example, SDCZ73-128G for SanDisk Ultra).

    2. Go to the manufacturer's website:

      • SanDisk: https://www.sandisk.com/about/fake-flash-memory
      • Samsung: https://www.samsung.com/semiconductor/minisite/ssd/global/html/support/validation.html
      • Kingston: https://www.kingston.com/ru/support/technical/genuine

  • Enter the serial number in the form check. If the site gives an error, you have a fake.

    • 💡 Advice: Buy flash drives only from official distributors or trusted sellers (for example, Citylink, M.Video, Amazon). Avoid marketplaces like AliExpress or Wish —the risk of running into a fake there 60%.

    Frequent errors and their solutions

    Sometimes a flash drive does not work correctly not because of a counterfeit, but because of others reasons. Understandable problems and ways to solve them:

    Problem Possible cause Solution
    Flash drive not detected Incompatible file system (NTFS, ext4) Format to FAT32 or exFAT via PC
    Shows a smaller volume Hidden section for functions like Secure Folder (on Samsung) Use SD Insight to analyze the structure
    Error "Damaged SD card" Incorrect extraction or file system failure Check on PC via chkdsk (command: chkdsk E: /f, where E: is the letter of the flash drive)
    Slow recording (less than 5 MB/s) Fake controller or worn out memory cells Check through CrystalDiskMark; if the speed is not restored, replace the flash drive
    The flash drive is heating up Controller defect or overload (for example, recording 4K video) Stop using, check on the PC; if the heating persists, dispose of it

    🔧 If the flash drive is detected as 0 bytes:

    1. Do not format it immediately! data-i="301">or Recuva or TestDisk.

    2. Check in Disk Management (Windows): if the drive appears as "Not distributed", create a new partition.

    3. If all else fails, the flash drive is physically damaged. In this case, data recovery is possible only in specialized laboratories (cost from 5,000 rubles).

      4. 💡

      If the flash drive is no longer detected after falling or contact with water, do not dry it with a hairdryer or in rice! This will worsen the damage. It is better to put it in a bag with silica gel (from the boxes with shoes) for 24 hours, and then try to connect.

      FAQ: Answers to frequently asked questions

      🔹 Why does the smartphone show that the flash drive is 128 GB, but only 119 GB is available?

      This is normal! data-i="312">(1 GB = 1,000,000,000 bytes), and operating systems count in decimal volume (1 GB = 1,000,000,000 bytes), and operating systems count in binary gigabytes (1 GiB = 1,073,741,824 bytes). The difference of ~7% is not a cheat, but a feature of the calculation. In addition, part of the space is occupied by the file system (for example, FAT32 reserves ~1-2% of the volume).

      🔹 Is it possible to check the capacity of a flash drive without connecting to a PC?

      Yes, standard Android tools or applications are enough for this like SD Insight and A1 SD Bench. However, for deep diagnostics (for example, a test for the authenticity of a controller) you will still need a computer with apps ChipGenius or H2testw.

      🔹 What to do if the flash drive is detected but not formatted?

      Possible causes and solutions:

      • 🔒 Write protection: Check the physical switch on the case (if any) or use the command in ADB: sm disk:179,64 public (replace the identifier with yours).
      • 🛠️ Damaged file system: Connect to a PC and execute chkdsk E: /f (where E: is the drive letter).
      • 🚫 Hardware failure: If The flash drive is not formatted on any device - it is faulty.
    🔹 How to check the flash drive if it is used as internal memory (Adoptable Storage)?

    If you configured the flash drive as internal memory expansion (function Adoptable Storage), standard verification methods will not work. You need:

    1. Disable Adoptable Storage in settings (Settings → Storage → [Flash drive name] → Disconnect).

    2. After disconnecting, the flash drive will be formatted and can be checked using standard methods.

    ⚠️ Attention: Disconnection Adoptable Storage deletes all data from the flash drive Make a backup copy first! data-i="346">Attention:

    🔹 Why do they disappear or become damaged after writing files to a flash drive?

    This is a classic sign fake flash driveSuch drives have a real capacity that is much less than stated. (for example 4 GB instead of 128 GB). When you write files beyond the real limit, they are:

    • Or overwritten over old data (therefore disappearing).
    • Or damaged due to controller errors.

    You can check this using H2testw (on PC) or FakeFlashTest (on Android). If the test confirms a fake - do not use this flash drive to store important data!