Fixed: SD Card Unallocated Space Cannot Format [3 Ways]

Here are various reasons to explain why SD card unallocated space cannot format, and there are ways to fix the problem with free AOMEI Partition Assistant.


By Michael / Updated on May 12, 2023

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Why cannot format SD card unallocated space?

You may encounter a similar situation that you have an 8GB micro SD card that somehow got formatted to 4GB leaving the other 4GB unallocated. Anything you’ve tried seems you can’t format unallocated space on SD card. And Disk Management won’t do anything to fix this problem.

Why SD card unallocated space cannot format? Maybe, some readers or host devices are not compatible with the larger SDHC and SDXC card, and this leads to re-partition the SD card to a size supportable. In addition, invisible shadow files, formatting overhead, and hidden recovery partition also cause the problem that you can’t format unallocated space on SD card. But you don’t need to worry, a third-party software as AOMEI Partition Assistant Standard is the solution to the problem.

How to fix "SD card unallocated space cannot format" issue

AOMEI Partition Assistant is a free and powerful software being compatible with all Windows editions including Windows 7/8/8.1/10/Vista/XP of both 32bit and 64bit. There are three ways to fix the problem with it, and you should free download this program first.

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Method 1: Extend the first partition into the unallocated space

Step 1. In the main interface, right-click the first partition and then select “Resize Partition”.

Resize Partition

Step 2. In the pop-up window, drag the right slider rightwards to extend to full capacity.

Extend Partition

Step 3. Now you can preview the result and do remember to click “Apply”.


Method 2: Create a new partition using the unallocated space

If you want more than one partition, then you can format the unallocated space to create a new one directly.

Step1. Right-click the unallocated space and select “Create Partition”.

Create Partition

Step2: In pop-out window, set the basic information for the new partition.


Step 3: click “Apply”.

Method 3: Delete the existing partition and create a new one using the whole unallcoated space

Deleting the existing partition will erase all data on it, so you should backup first. Then you can make use of the whole 8GB to create a new partition.

Step1. Right-click the existing partition and select “Delete Partition” and follow the prompts to delete the existing partition. 

Step 2.  Right-click the 8GB unallocated space and select “Create Partition”.



Step 3. Set partition information in a pop-up window.

Step 4. Click “Apply”.

Now, choose a method you do prefer to fix the problem that SD card unallocated space cannot format. Also, you can use AOMEI Partition Assistant to restore USB drive back to full capacity.

Michael · Staff Editor
Michael is a professinal editor of AOMEI editor team.