Why Disk Management and File Explorer Show Different Sizes

What are these two tools?

Disk Management shows the physical disk and how it is divided. A disk can be split into parts called partitions. Each partition is like a room in a house. File Explorer shows the drives you use, like C: or D:, and how much space is used or free.

Why the numbers differ

• Different units. Disk makers count 1 GB as 1,000 million bytes. Windows counts 1 GB as 1,024 x 1,024 x 1,024 bytes. So a "500 GB" disk shows about 465 GB in Windows.
• Hidden partitions. Disk Management shows small system partitions, such as Recovery or EFI. File Explorer does not show them as drives. They take a little space.
• Space used by the file system. The file system is the way Windows organizes data on a disk. It keeps some space for its own records.
• Hidden and system files. Files like the page file, hibernation file and System Volume Information use space. File Explorer may not count them when you check a folder.
• Shadow copies and restore points. These are saved snapshots of your disk. They use space but you do not see them as normal files.
• Unallocated space. This is free disk space not yet turned into a drive. Disk Management shows it in black. File Explorer cannot show it.

Steps to check

1. Press Windows + X and click Disk Management.
2. Look at each disk. Note the size of each partition and any black Unallocated block.
3. Open File Explorer and click This PC.
4. Right-click a drive and choose Properties to see used and free space.
5. Add the partition sizes from Disk Management. The total should be close to the full disk size.

See hidden files

1. In File Explorer, click the View tab.
2. Click Show, then tick Hidden items.

You will see more files, but some system folders still stay locked.

If you want the unused space

If there is unallocated space, you can right-click it in Disk Management and choose New Simple Volume. Or right-click a drive and choose Extend Volume if the free space is next to it.

Quick recap

• The two tools measure things in different ways.
• Unit differences, hidden partitions and system files explain most gaps.
• A small difference is normal.
• Back up before you change any partition.