Like in previous versions of the Windows operating system, the Disk Management tool in Windows 10 enables you to create, format, delete, shrink and extend partitions without the help of third-party software. In one of our previous guides titled how to extend a partition in Windows 10, we discussed extending the system partition using the Disk Management tool as well as third-party utility. While trying to extend system or any other partition using the built-in Disk Management utility, you might see that the Extend Volume option, which appears when you right-click on a partition, is grayed out or disabled. In short, the Disk Management might not allow you to extend a partition even if you have unallocated space on the drive. If the Extend volume option is not clickable or grayed out, it could be because of one of the following reasons. The solution is mentioned at the end of this article. Reason 1 of 4 You are trying to extend FAT or FAT32 partition Yes, the Extend volume feature applies only to the NTFS partitions. In other words, Windows doesn’t support extending FAT and FAT32 file systems out of the box. If you want to extend FAT or FAT32 partition, you need to use third-party tools like MiniTool Partition Wizard free edition. Here is how to check if a partition is formatted with FAT, FAT32 or NTFS: Step 1: Open This PC. Right-click on the drive that you want to check, and then click Properties. Step 2: Under the General tab, you can see the current file system next to the File System. In the picture, the drive is formatted with NTFS. If you want to extend a FAT or FAT32 partition, either use MiniTool Partition Wizard free software or convert FAT/FAT32 to NTFS first. Reason 2 of 4 There is no unallocated space on the drive Many of you might aware of this but most users are not aware of the fact that there must be unallocated or unpartitioned space on the drive in order to use the Extend volume feature. Just because there is GBs of free space on one of your partitions, you can’t extend a volume using free space available on another partition. If you have free space on one partition, you need to shrink the partition first to create some unallocated space and then use the Extend volume feature. Reason 3 of 4 The unallocated space is not to the right of the partition that you want to extend At times, even if you have GBs of unallocated space on the drive, Windows 10 won’t display the Extend volume option as the unallocated space is not after the partition that you want to extend. The unallocated space must immediately follow the volume or partition that you want to extend. Let’s say that the unallocated space is after the “C” drive and before the “D” drive. So, in this case, the unallocated space is after the “C” drive and there is no unallocated space immediately after the “D” drive. Because of this, when I right-click on “C” drive/partition, Windows displays the Extend volume option. The same option is grayed out when I right-click on the “D” drive because the unallocated space is not immediately after the “D” drive. In the picture below, the unallocated space is to the right of the partition “C”, and Windows allows me to extend the “C” drive without any issues. Once again, in this situation, we recommend using the excellent MiniTool Partition Wizard free edition to extend your partition without any issues. Reason 4 of 4 The unallocated space is not in the extended partition If you’re trying to extend a logical drive on a basic disk, please remember that the unallocated free space must be in the extended partition that immediately follows the logical drive. In simple words, if you’re unable to extend a volume or partition using Disk Management, please use the MiniTool Partition Wizard free edition. If your PC is unbootable, create MiniTool Partition Wizard bootable USB, boot from the USB, and then extend the partition. How to extend a partition when the option is grayed out Since Windows 10 doesn’t allow you to extend a partition or volume under all conditions, you can use a free partition manager software to extend a partition without any issues. Here is how to extend a partition using the MiniTool Partition Wizard Free Edition. Step 1: First of all, download the Minitool Partition Wizard Free version from this official page and install it on your computer. Step 2: Launch MiniTool Partition Wizard. It requires admin privileges. Step 3: On the home page of the software, click on the Disk and Partition Management tile. Step 4: Now, right-click on the partition that you want to extend and then click the Extend option. Step 5: In the resulting dialog, select a partition from where you would like to move the free space to the partition that you want to extend, select how much free space you want to take from the selected partition (move the slider to select the space) and then click the OK button. Step 6: Finally, click the Apply button to begin extending the partition. If you get the following dialog, click the Yes button. The software may take a while to complete the operation.