How to Check Folder Sizes in Windows File Explorer

Why Explorer won't just show the number

A file carries its size in NTFS metadata, so displaying it is free. A folder's total is stored nowhere: to show it, Windows would have to open every subfolder and add up every file, on every refresh, in every window. Multiply that by thousands of folders on a slow drive and you see why Microsoft left the column blank rather than keep the disk permanently busy.

The hover tooltip shows a single folder's size without opening the Properties dialog, but it works one folder at a time and recalculates on every hover. One nuance worth knowing: Properties lists both Size and Size on disk, and the second is the number that matters for free space — it counts cluster overhead, so thousands of small files can eat far more disk than their raw sizes suggest.

Four ways to get sizes inside Explorer

For most questions the built-in tools are enough, and they need no downloads. The one trick to memorize: while a normal view leaves the Size column blank for folders, search results fill it in — searching a parent folder forces Explorer to walk everything beneath it, and that walk is exactly what produces the numbers.

• Right-click → Properties — exact size of one folder, subfolders included; select several folders first (Ctrl+click) and Properties shows the combined total
• Hover tooltip — rest the mouse on a folder for a second; one number, zero clicks, no subfolder breakdown
• The search trick — open the parent folder, type * in the search box, wait for the results, then right-click a column header → Size and sort; folders now display real sizes
• Settings → System → Storage — a category breakdown (apps, temporary files, documents) for every drive, no Explorer needed

PowerShell and scanners for whole-drive maps

When you need every top-level folder ranked at once, PowerShell does it without third-party tools. Open Windows Terminal and measure with Get-ChildItem and Measure-Object: for example, Get-ChildItem D:\ -Directory | ForEach-Object { [PSCustomObject]@{ Folder = $_.Name; GB = [math]::Round(((Get-ChildItem $_.FullName -Recurse -Force -ErrorAction SilentlyContinue | Measure-Object Length -Sum).Sum)/1GB, 2) } } | Sort-Object GB -Descending prints a ranked table of the folders on D:. On a full SSD it takes a minute or two; the -Force switch makes hidden and system files count too.

For recurring audits, dedicated scanners are faster because they read the NTFS master file table directly instead of opening file after file: WizTree paints a whole drive in seconds, TreeSize Free gives a sortable tree, and WinDirStat draws the classic treemap — slower, but great for spotting one giant blob. Once you know what is eating the space, a cleanup pass over caches, downloads and temp files — by hand or scheduled in a tool like Kleaner PRO — keeps the drive from filling right back up.

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