By Emily / Last Updated April 30, 2019

About “New SSD reports wrong size”

Thanks to the optimal reading&writing performance and low latency, SSD (solid state drive) is becoming increasingly popular, and it has been a prior choice for computer users. Some users even migrat OS to SSD for a quick boot time.

However, after they bought SSD and began to use, most of them would find the SSD shows wrong size, and no reasons could be found. So what causes the issue that the actual capacity does not match the described capacity?

Causes for discrepancy between actual capacity and described capacity of SSD

As for the SSD drive showing half space or wrong space, what’s the first thing that comes to mind? I believe most users would thought they have bought a fake, damaged or corrupted SSD from unscrupulous sellers. Besides that, there are 3 reasons for the discrepancy between actual and described capacity of SSD/HDD.

  • Vendor's capacity calculation is different from computer OS

  • The Virtual Memory paging file is located on the SSD/HDD

  • Disk is initialized to be MBR

Then, how to deal with these three problem? Read on to get the answers.

Solutions to “SSD reports wrong size”

After figuring out possible reasons for SSD showing wrong space, it’s time to get a deeper understanding of each one and check the corresponding solutions.

Solution 1. Make a conversion between vendor's and operating system's capacity calculating method

It is well known that computers operate in binary (or base-2), which is a numeric system that only use two digits: 0 and 1. As a result, in the operating systems, the capacity is calculated on a one-step basis every 1024, so every 1024MB is 1GB, and every 1024GB is 1TB. But the hard disk manufacturers calculate the capacity on a one-step per 1000, that is to say, every 1000MB equals 1GB and every 1000GB equals 1TB, which leads to the “reduction” of SSD capacity.

For example, we buy an SSD advertised as 120GB, but it will only show about 112GB available for usage in the computer operating system. Therefore, when you find the SSD descried capacity is not same as the actual one, you can convert the capacity according to following calculation method.

NOTE: actual capacity= byte/(1024*1024*1024 *1024)

Take 120GB as an example:

In manufacturer capacity calculating: 120GB=120,000MB=120,000,000KB=120,000,000,000 bytes

Actual capacity (in computer operating system)=120,000,000,000/(1024*1024*1024)≈111.8GB

So, the actual capacity of an SSD labeled as 120GB is just about 112GB.

Solution 2. Reset the Virtual Memory paging file

Storage/memory is quite important for computers. All programs running in the computer need to be executed in memory. So if the executed programs are too large or there are multiple programs running at the same time, the memory will run out quickly.

In order to fix this problem, Windows adopt “Virtual Memory” (also Virtual Storage) technology, which means taking out some space of hard disk to work as memory supporting programs’ running. Such space is called Virtual Memory. In the hard disk, the virtual memory exists as the PAGEFILE.SYS.

The size of the Virtual Memory in the computer is exactly how much space it takes up in the hard disk. So if you find the actual size of SSD is different from the described one, you can check and reset the size of the virtual storage in the computer taking the steps below.

Step 1. Right-click “My Computer/This PC” and choose “Properties”.

Step 2. Click “Advanced system setting” in the left panel--> “Advanced” in the next mini window--> “Settings” under “Performance”.

Virtual Memory

Step 3. In the “Performance Options” windows, locate “Advanced” and click “Change”.

Step 4. Locate the drive letter of SSD, deselect “Automatically manage paging file size for all drive”, tick “Custom size” and enter the initial size and maximum size, and then click “Set” and “OK”.

Reset Virtual Memory

Step 5. Finally, reboot your computer.

Then, you can allocate the size of Virtual Memory according to your computer's situation. Setting a certain size of virtual memory will greatly benefit the smooth operation of the system, so it is not advised to cancel virtual memory directly.

Solution 3. Convert MBR to GPT

MBR and GPT are two different disk types, their main difference lies in the partition structure and partitioning methods. However, the MBR only works with disks up to 2 TB in size, so it cannot recognize the rest space of SSD surpassing 2TB, which could also lead to the SDD reports wrong size. If it is the case, you can convert MBR to GPT through the below two methods.

Method 1. Using Diskpart (data loss)

NOTE: this method will erase all data on the SSD, so please back up files that are important in advance.

After making a backup, then press “Win+R” simultaneously to open “Run”, type “diskpart” and hit “OK”. Then input the following command:

(1) list disk

(2) select disk 1(replace “1” with the disk number of your SSD)

(3) clean: delete all partitions on the chosen SSD drive and cause data loss.

(4) convert gpt

Diskpart Convert GPT

Then, your MBR SSD is converted to GPT successfully, and the rest space over 2TB can be recognized now.

Method 2. Via freeware- AOMEI Partition Assistant (Without Data Loss)

As mentioned above, the Diskpart will require you to delete all partitions first on the SSD, then you can convert it to GPT successfully. So it is highly advised to convert MBR to GPT using a third-party converting tool: AOMEI Partition Assistant. It can convert any data disk from MBR to GPT, or GPT to MBR without deleting partitions, so you don’t need to take a risk that you will lose everything important.

Warning: in order to avoid data loss caused by some uncontrollable factors such as sudden power failure, making a backup is always suggested at any time.

(1) Download the freeware, install and run it, right-click the SSD and select “Convert to GPT disk”

Convert 4TB To GPT

(2) It will pop out a window to confirm the operation. Click “OK”.


(3) Back to the main interface, you can confirm the operations again, if there is no problem, click “Apply” on the toolbar.

4TB Apply


With the causes and solutions illustrated in detailed above, now you know how to do when SSD reports wrong size. If the SSD is the boot disk, you need to upgrade to AOMEI Partition Assistant Professional, which allows you to convert system disk between MBR and GPT without data loss.