USB drive showing Unknown Capacity? Cannot Format Error Occur

In the ever-expanding digital world, storage is one of the primary tools to facilitate the safe movement of data; while cloud storage is getting increasingly popular, there is no doubt that conventional storage mediums, like USB drives, are still prevalent. Due to unknown reasons, you may have encountered the issue of a USB drive showing unknown capacity, not being able to format a USB drive, or a USB drive showing less capacity. In this article, we will look at how to fix a USB drive showing Unknown Capacity; Cannot Format.

USB drive showing Unknown Capacity; Cannot Format

USB drive showing Unknown Capacity? Cannot Format Error Occur

While there can be many unrecognizable hardware reasons for your USB drive showing unknown capacity, it cannot format, most of the time, it is related to the formatting and partitioning of the USB drives. Here are the reasons for the error to occur:

  • Write protection: This prevents the USB drive from being modified or erased and can be due to a physical switch, a software setting, or a virus.
  • Hidden partitions: These are not recognized by Windows and can be due to a different file system, a bootable disk, or a recovery partition.
  • Bad sectors or corrupted files: These are errors on the USB drive that prevent it from being appropriately formatted and can be due to improper removal, power failure, physical damage, or viruses.
  • Wrong file system: This file system is incompatible with Windows or has a size limit, such as FAT32, which can only support partition sizes up to 32GB.
  • Unallocated space: This is not assigned to any partition and can be due to a previous resizing, shrinking, or deletion of sections.

Now that you understand the reasons for this error, let’s learn how to fix it.

How To Fix USB drive showing Unknown Capacity; Cannot Format

In this section, we will look at some methods to fix the USB drive showing an unknown capacity cannot format error. Here’s all that’s covered:

  1. Disk Management tool
  2. Disk Tool Command

Let’s now proceed with looking at each of these methods in detail.

1] Disk Management Tool

The Disk Management tool in Windows is used to manage disk partitions, format partitions, individual disks and drives, and many other disk management functions. If your drive is showing unknown capacity, the chances are that it has an unallocated volume.

This means the space is available but is yet to be allocated for use. Here’s how to create a simple volume to use a USB drive in the Disk Management tool:

  • Open the Windows start menu and search for Disk Management.
  • Now, open the first option, i.e., Create and format hard disk partitions.
  • A disk management window will open. In the bottom end of the window, you will see your USB drive and its size as unallocated.
  • Right-click the drive and select New Simple volume from the menu. The New Simple Volume wizard will open, and proceed with the next button. Create a new simple volume to alloccate space in USB drive in Windows
  • On the next page, you will be asked to assign a size to the volume and assign the size equivalent to the maximum disk space. Assigning volume size in new smple volume wizard in disk management
  • Now, you will be asked to select a drive letter. Select any from the drop-down menu. Selecting a drive letter for new simple volume in Windows Disk Management
  • In the following menu. Select the Format this volume with the following settings. Then select the File system as Exfat, Allocation Unit Size as default, and volume label as anything you prefer.  Selecting formatting option for new simple volume in disk management
  • Review the options you selected on the final screen and click on finish. This will create a new simple volume on your drive, and you can now access it completely.

2] Disk Part Command

The Disk Part command in the command prompt is also used for the same purpose as the Disk Management tool; it provides additional functionality on top of the Disk Management tool. If you cannot format or access your drive, you must first clean the drive of any file system and volumes, then reassign the file system and partition. Here’s how to do it:

  • In the Windows start menu, search for Command prompt, right-click the first options, and select Run as Administrator.
  • Make sure that you have the USB drive plugged in. Now type Diskpart and press enter. This will launch the Disk Part tool.
  • Now type list disk and press enter. This will list all the disks that are available on your PC. Take note of the Disk number of your USB drive.
  • In the next step. Type. select disk x , where x is the disk number you noted in the previous step(For example, if it was 1, you type select disk 1). This step will select the disk and help you perform actions specific to that disk.
  • Now, type clean and press enter. This will erase all your drive’s partitions, data, and file systems. Before performing this step, ensure you have selected the correct drive.
  • After this, type create partition primary and press enter. This will create a primary partition for your drive.
  • Now, type format fs=exFat . This will format the drive to the Exfat file system, the fastest and most widely used one. Clean and reformat a USB drive using command prompt
  • After this, type exit and press enter.

This will reformat your drive; you can now access it through the file manager.


In this article, we learned how to fix a USB drive showing Unknown capacity and cannot Format. USB drives are not as complex as they seem, and software issues with almost all USB drives can be fixed quickly using a few inbuilt utilities in Windows. We hope you found the article to be helpful. Please make sure that you share it with everyone.


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