How to Check Your Outlook Folders and Sizes

Reduce your Outlook folder sizes by finding the largest emails

Information overload vector concept

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Outlook can become slow and unwieldy when its folders accumulate large emails and attachments. To help remedy this situation, Outlook comes with a tool that shows how much space each folder occupies. By checking the size of each folder and subfolder, you can identify which account is using up the most space, as well as the subfolders that contain large files. Here's how to learn how big your email folders have grown in Outlook and take action if they are too big.

Instructions in this article apply to Outlook 2019, 2016, 2013, 2007; and Outlook for Microsoft 365.

Checking Your Folders

To see the size of your folders in Outlook:

  1. Right-click the folder you want to check, and select Data File Properties. In Outlook 2019, select Properties.

    Screenshot of Data File Properties in Outlook
  2. Select Folder Size.

    Screenshot of the Folder Size button in the Folder Properties window
  3. The Folder Size dialog box shows the size of the folder and its subfolders in kilobytes.

    Screenshot of folder size window in Outlook

If you use Outlook 2007:

  1. Select Tools > Mailbox Cleanup.

  2. Select View Mailbox Size.

  3. Select Close (two times) to close the mailbox size view again.

Reduce the Size of an Outlook File by Archiving Mail

Archiving old or less frequently accessed messages is an easy way to keep the sizes of your Outlook folder and files manageable. Outlook can even do the archiving automatically.

Find the Biggest Emails in Your Outlook Folders

To have Outlook gather all the largest emails in all your folders:

  1. Select the Search Current Mailbox text box, or press Ctrl+E.

    Screenshot of the search ribbon in Outlook
  2. Go to the Search tab.

  3. In the Options group, select Search Tools > Advanced Find.

    Screenshot of Search Tools in Outlook
  4. In the Advanced Find dialog box, select the Look dropdown arrow and choose Messages.

    Screenshot of Advanced Find in Outlook
  5. To search more folders than the inbox (or whichever folder is currently open in Outlook's main window), select Browse. Select the check box next to the folders you want to search, and select the Search subfolders check box. Select OK.

    Screenshot of selecting folders in Outlook
  6. In the Advanced Find dialog box, go to the More Choices tab.

  7. Select the Size (kilobytes) dropdown arrow, choose greater than, then enter a size (such as 5000 for folders greater than 5 MB).

    Screenshot of Advanced Find in Outlook
  8. Select Find Now.

  9. Double-click a message to open it and deal with it as you see fit. Or, select Delete in the search results to delete any message right away.