How to Compare Two TreeSize Scans Reliably | TreeSize Windows Guide

Quick answer

Use the same scan path, account permissions, size metric, filters and approximate workload. Compare total bytes and specific folder changes, not just the visual percentage bars.

This is a read-first troubleshooting guide, not a guarantee that a particular file can be removed. Verify ownership and backups before changes.

Step-by-step workflow

Step 1. Record the selected root path, date, TreeSize edition and whether the scan was elevated.
Step 2. Use the same Size or Allocated Space metric for both measurements.
Step 3. Run both scans under comparable workload conditions, ideally avoiding active imports or backup jobs.
Step 4. Compare the same folders and export results when the edition supports it.
Step 5. Investigate the changed directories before removing files; growth in logs or caches can be expected.

What can go wrong

Relative percentages can change without a folder growing.
Access-denied content can make totals unreliable across accounts.
Hard links or cloud placeholders can complicate comparisons.

Frequently asked question

Can a scan comparison prove a folder has leaked storage?

No. It identifies growth; you still need to inspect the owning process and normal retention behavior.

Related reading

Editorial method and sources

This guide distinguishes observed disk usage from safe cleanup actions. Its recommendations are based on Windows storage behavior and documented workflows; vendor capabilities and licensing can change.

Prepared by jam-software.org Editorial Team. Published October 28, 2026. Sources and corrections.

Right-click Properties

Right-click any folder and choose Properties. Windows walks every file inside it and reports a total under Size and Size on disk. This is accurate, but it's a one-folder-at-a-time answer: you have to already suspect the folder is large before you check it, and a big folder with many subfolders can take a noticeable moment to finish counting.

It's fine for confirming a single suspicion — "is this game install really 80 GB?" — but it doesn't help when the question is "where did 60 GB on my C: drive go," because you'd have to check dozens of folders one by one to find the answer.

Details view and the Size column

Switch Explorer to Details view (View > Details) and you'll see a Size column. For files, this works exactly as expected. For folders, Explorer usually leaves the cell blank instead of showing a total.

That's not a bug — Explorer's folder listing doesn't pre-calculate folder contents, because doing so for every folder in a large directory would be slow. The Size column only reports what it already knows, which for a folder is nothing until you ask it directly, as in the Properties method above.

A PowerShell command that totals a folder

If you'd rather script it, Get-ChildItem combined with Measure-Object gives you a folder's total size without opening Explorer at all. Open PowerShell and run:

(Get-ChildItem -Path "C:\Users\YourName\Downloads" -Recurse -File -ErrorAction SilentlyContinue | Measure-Object -Property Length -Sum).Sum / 1GB

That command recurses through every file, sums the Length property in bytes, and divides by 1 GB so the result is readable. -ErrorAction SilentlyContinue matters here: without it, the command stops and prints an error the first time it hits a folder your account can't read, such as a system-protected path.

This is accurate and scriptable, but it's still a single-folder answer, and on a folder with hundreds of thousands of files it can take a while to finish because PowerShell isn't optimized for bulk directory enumeration the way a dedicated scanner is.

A tree analyzer for whole-drive answers

When the real question is "which folder, anywhere on this drive, is responsible for the missing space," a folder-size tool such as TreeSize is a better fit than repeating any of the methods above by hand. It scans the whole tree once, sorts every folder by size, and lets you drill from the drive root down to the exact subfolder that's heavy — see how to use TreeSize for the full walkthrough.

The TreeSize Free download is enough for this kind of one-off audit on a personal PC. If you need to repeat the scan on a schedule or across several machines, that's a TreeSize Professional job instead.

Hidden and system files can skew the total

By default, Explorer hides files and folders marked hidden or protected-system, which means a folder total you get by eyeballing visible files will be lower than the real size. Properties and PowerShell both count hidden files correctly as long as your account has permission to read them, but a manual visual estimate will not.

System-protected folders under C:\Windows and C:\ProgramData in particular can report as smaller than they are if a scan runs without elevated permissions — see running TreeSize as administrator for why that happens and how to fix it.

Folder size FAQs

Why does a folder show a blank Size in Explorer's Details view?

Explorer doesn't pre-calculate folder totals when listing a directory, since doing that for every row would slow the listing down. Use Properties or a scan tool to get an actual total.

Does Get-ChildItem count subfolders automatically?

Why does PowerShell give an error partway through a scan?

Is the size shown in Properties the same as the size on disk?

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Last reviewed by the jam-software.org editorial team on September 15, 2026. Spotted something out of date? Tell us.