Fix TreeSize Reporting a Different Size Than Disk Properties on Windows 11

When you compare the folder or file size shown by TreeSize with the size shown in Windows 11 Disk Properties, you often see a discrepancy. This difference can be several megabytes or even gigabytes, which creates confusion about which tool is accurate. The mismatch typically occurs because TreeSize and Windows Explorer count files in fundamentally different ways — TreeSize includes hidden system files, symbolic links, and junction points by default, while Disk Properties uses the NTFS compressed size or excludes certain metadata. This article explains why the numbers differ and provides step-by-step fixes to make TreeSize match Windows 11 Disk Properties.

Why TreeSize and Disk Properties Show Different Sizes on Windows 11

TreeSize is a third-party disk space analyzer that scans folders and drives at a raw file-system level. By default, it counts every file and folder it encounters, including hidden system files, reparse points, and junction points. Windows 11 Disk Properties, accessed by right-clicking a drive or folder and selecting Properties, calculates size using the NTFS file system API. This API applies compression, deduplication, and sparse file handling before reporting the final number.

The core technical root cause is that TreeSize defaults to reporting allocated space on disk, which includes slack space — the unused portion of the last cluster assigned to a file. Windows Disk Properties reports the logical size, which is the actual file content size without slack. For example, a 1 KB file on a 4 KB cluster uses 4 KB of allocated space but shows 1 KB in Disk Properties. Over thousands of files, this difference adds up significantly.

Hidden System Files and Junctions

Windows 11 Disk Properties excludes certain system-managed files, such as the pagefile.sys, hiberfil.sys, and the System Volume Information folder. TreeSize, unless configured otherwise, includes these items in its scan. A junction point like Documents and Settings, which is a symbolic link to C:\Users, can be counted twice by TreeSize if the scan follows the junction into the same physical data.

Compression and Deduplication

NTFS compression reduces the on-disk size of files. Windows Disk Properties reports the compressed size. TreeSize, by default, reports the uncompressed logical size or the allocated size before compression. If you have enabled NTFS compression on folders, the discrepancy grows larger.

Steps to Make TreeSize Match Windows 11 Disk Properties

The following steps configure TreeSize to use the same counting rules as Windows 11 Disk Properties. Apply these settings before running a scan for accurate comparisons.

1. Open TreeSize and access Options
   Launch TreeSize as an administrator. Click the Options menu at the top and select General from the dropdown. This opens the main configuration window.
2. Set counting mode to Logical size
   In the General Options window, locate the Counting rules section. Change the dropdown from Allocated space to Logical size. This tells TreeSize to report the actual file content size, excluding slack space. Click Apply.
3. Exclude hidden system files
   In the same General Options window, check the box labeled Exclude system files under the Exclusions group. This prevents TreeSize from counting files like pagefile.sys and hiberfil.sys, which Windows Disk Properties ignores. Click Apply.
4. Disable junction point following
   Click the Scan menu at the top and select Scan options. Uncheck Follow junction points. This stops TreeSize from traversing symbolic links that point to already-scanned folders. Click OK.
5. Enable compressed size reporting
   Return to Options > General. In the Display section, check Show compressed size. This forces TreeSize to display the NTFS compressed size for compressed files, matching what Disk Properties shows. Click Apply and then OK.
6. Rescan the drive or folder
   Right-click the drive or folder you want to compare and select Rescan. Wait for the scan to complete. The sizes shown in TreeSize should now closely match the values in Windows 11 Disk Properties.

If TreeSize Still Reports a Different Size After Configuration

Even after applying the changes above, a small difference of a few kilobytes may remain. This is normal and comes from how each tool rounds file sizes or handles metadata like alternate data streams. If the difference exceeds 1% of the total folder size, check these additional factors.

TreeSize Shows a Larger Size Than Disk Properties

If TreeSize still reports a significantly larger size, verify that you have not excluded the Recycle Bin or System Volume Information folders. TreeSize may still be scanning these if the exclusion list is incomplete. Open Options > General > Exclusions and add the following paths:
C:\$Recycle.Bin
C:\System Volume Information
Click Apply and rescan.

TreeSize Shows a Smaller Size Than Disk Properties

This situation is less common and usually occurs when TreeSize is configured to skip files larger than a certain size. Go to Options > General > Scan limits and ensure Skip files larger than is set to Disabled. Also check that Skip files smaller than is set to 0 KB.

Difference Persists After All Settings Are Applied

Open Windows 11 Disk Properties for the same folder and note the Size on disk value. TreeSize may be reporting allocated space instead of logical size if the setting did not save. Repeat the steps in the previous section and close all TreeSize windows before reopening the application. Run the scan again from a fresh launch.

TreeSize Counting Modes vs Windows Disk Properties: Comparison Table

Item	TreeSize Default	Windows 11 Disk Properties
Counting method	Allocated space on disk	Logical file size
Slack space included	Yes	No
Hidden system files	Included	Excluded
Junction points followed	Yes	No
NTFS compression handled	Uncompressed size	Compressed size
Alternate data streams counted	Yes	No

You can now configure TreeSize to report sizes that match Windows 11 Disk Properties by adjusting the counting mode, excluding system files, and disabling junction point following. After applying these settings, rescan your folders to verify the numbers align. For fine control over specific folders, use TreeSize’s exclusion list to skip the Recycle Bin and System Volume Information. An advanced tip: save your configuration as a profile by going to Options > Save profile and name it “Disk Properties Match” so you can reload it for future scans without re-entering each setting.