Windows Shows 2TB Instead of 12TB, Why and How to Fix

I have a 12TB Seagate ST12000VN008 HDD. In Windows, it shows 2TB instead of the full capacity of the drive. This is the second hard drive Seagate sent me. So I think it's not the hard drive but something on my computer. Any help in resolving this issue is greatly appreciated.

This happens mainly because your 12TB hard drive is initialized to MBR. If you look at the partition style, you will find that it is MBR (Master Boot Record), not GPT (GUID Partition Table). On an MBR disk, these errors, like a 4TB hard drive showing as 2TB or a 3TB hard drive only showing as 2TB, are common. To fix this error, you need to convert MBR to a GPT. Follow the steps below to try:

Step 1. Press the Win and R keys, type cmd, and hit Enter to launch the command prompt.

Step 2. Type diskpart and press Enter. Type the following commands in order; remember to press Enter after each one.

1. list disk
2. select disk n(n represents the drive letter of your 12TB drive)
3. clean
4. convert gpt

Step 3. Type exit when the conversion is complete.

However, as you can see, the command "Clean" will wipe all the data on your hard drive, so if you have important documents on this hard drive, turn to EaseUS Partition Master.

This tool can help you convert MBR to GPT without any data loss. Here are the steps:

Step 1. Launch EaseUS Partition Master and click "Disk Converter."

Step 2. Choose "convert MBR to GPT" in this window and click "Next."

Step 3. Choose your 12TB hard drive and click "Convert."

Without typing any commands, you can convert MBR to GPT without data loss. Based on my past test, this tool works well.