Outlook View Folder Size: How to Check It
This article explains how to check the size of folders in Microsoft Outlook, what the numbers mean, and how to manage your mailbox storage effectively. You’ll learn the built-in methods for viewing folder sizes in Outlook desktop, web, and mobile apps, along with common pitfalls and practical tips.
Why Folder Size Matters in Outlook
Mailbox storage limits are a common source of frustration. When your mailbox approaches its quota, you may see warnings, lose the ability to send or receive mail, or find that Outlook runs slowly. Knowing which folders are consuming the most space helps you target cleanup efforts—deleting or archiving large emails instead of guessing. Folder size data also reveals patterns, such as a single oversized attachment in a sent item, or a growing archive folder that you thought was under control.
How to View Folder Sizes in Outlook Desktop (Windows)
Outlook for Windows does not show folder sizes in the default folder list. You must use the Folder Size dialog, which is hidden in the File menu.
- Click File in the top-left corner.
- Click Tools (or Account Settings in older versions) and then Mailbox Cleanup.
- In the Mailbox Cleanup dialog, click View Mailbox Size.
- A new window opens showing the total size of the mailbox and a breakdown by top-level folders (Inbox, Sent Items, etc.).
- To see subfolders, click Click here for details on folder size in the bottom-left corner of that window.
This method works for Exchange, Microsoft 365, and IMAP accounts. For POP3 accounts, the numbers may reflect only local data, not server content.
How to View Folder Sizes in Outlook on the Web (OWA)
Outlook on the web (the browser version) offers a simpler way to see folder sizes, but it is not immediately obvious.
- Right-click on a folder in the left navigation pane.
- Select Properties (or Folder properties).
- A dialog opens showing Total size and Subfolder size.
This works for individual folders, but there is no overall mailbox size summary in the same dialog. To see the total mailbox size, click the gear icon (Settings) → View all Outlook settings → General → Storage. This page lists the total used space and a breakdown by folder.
How to View Folder Sizes in Outlook for Mac
Outlook for Mac (classic version) shows folder sizes directly in the folder list if you enable the feature:
- Go to Preferences → General.
- Check the box for Show folder sizes.
- Close the preferences window. The size of each folder appears in gray next to the folder name.
This only shows the size of the folder itself, not subfolders. To see subfolder sizes, right-click a folder and choose Properties → Size.
How to View Folder Sizes in Outlook Mobile (iOS/Android)
Outlook mobile apps do not have a built-in folder size viewer. The app is designed for quick access, not storage management. To check folder sizes on a phone, you must use the web version (OWA) in a browser. Some users mistakenly look for a “storage� tab in the app—it does not exist as of the latest versions. The only workaround is to log into Outlook on the web from your phone browser and follow the OWA steps above.
Common Problems and Misconceptions
- Folder size shows 0 bytes: This often happens if the folder is an online archive or if the mailbox is not fully synced. Try sending/receiving to force a sync, or check the same folder in OWA.
- Size includes subfolders? In the desktop dialog, the size shown for a folder includes its subfolders by default. In OWA, the “Total size� includes subfolders, while “Subfolder size� is separate. In Mac, the folder list size does not include subfolders—you must open properties.
- Folder size vs. item count: A folder with 10,000 small emails may be smaller than one with 50 large attachments. Size is what counts for quota.
- Deleted items still count: Items in the Deleted Items folder count toward your mailbox size until they are purged. Empty the folder to free space.
What to Do When a Folder Is Too Large
Once you identify a large folder, you have several options:
- Delete old emails: Sort by date or size and remove what you no longer need.
- Archive: Use AutoArchive (desktop) or move items to a local .pst file.
- Remove large attachments: Save attachments to a cloud drive or local disk, then delete the original email.
- Empty Deleted Items: Right-click the folder and choose “Empty Folder�.
- Use Mailbox Cleanup: The same tool that shows sizes can find items older than a certain date or larger than a certain size.
Remember that archiving to a .pst file removes the data from the server, freeing quota, but the .pst file itself takes up local disk space.
Frequently Asked Questions
Why can’t I see folder sizes in Outlook desktop?
Because the folder list does not display sizes by design. You must use the Mailbox Cleanup tool (File → Tools → Mailbox Cleanup → View Mailbox Size). This is a deliberate UI choice to reduce clutter.
Does the folder size include subfolders?
In the desktop Mailbox Cleanup dialog, yes—the size shown for a folder includes all subfolders. In OWA, the “Total size� includes subfolders, while “Subfolder size� is separate. On Mac, the folder list size does not include subfolders.
Why does my folder size show 0 KB when I have emails in it?
This usually indicates a synchronization issue or that the folder is an online archive. Try pressing F9 to send/receive, restart Outlook, or check the same folder in Outlook on the web to confirm the actual size.
Can I see folder sizes in the Outlook mobile app?
No, the mobile app does not provide folder size information. Use Outlook on the web in a mobile browser instead.
How do I find the largest emails in a folder?
In Outlook desktop, sort the folder by “Size� column (right-click the column header to add it). In OWA, use the filter “Has attachment� and sort by size, or use the Mailbox Cleanup tool to find items larger than a specific size.
Does emptying Deleted Items free up space immediately?
Yes, but only after the folder is fully emptied. In Exchange/Microsoft 365, there may be a short delay before the server updates the quota.
Related
Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.