How to Check Your Outlook Folders' Sizes

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Find out how big your email folders have grown in Outlook—and take action if they are too big for their own good.

Is Your Outlook Slow and Unwieldy Lately?

Has handling email in Outlook become slow and unwieldy, or is your hard disk shrinking and you suspect the ten thousand three hundred ninety-one emails with their twenty thousand attachments (and then some) might be involved?

Which folder is to be blamed, though, and where do the big emails hide?

Fortunately, Outlook comes with a small tool that lets you find out exactly how much space each folder occupies on disk.

Check Your Outlook Folders' Sizes

To see the size of your folders in Outlook:

  1. Click on the root of the account or PST file you want to examine with the right mouse button.
  2. Select Data File Properties… from the menu.
  3. Click Folder Size….

Check Your Folders' Sizes in Outlook 2003 and 2007

To see the size of your Outlook 2003 or Outlook 2007 folders:

  1. Select Tools | Mailbox Cleanup… from the menu.
  2. Click View Mailbox Size….
  3. Click Close (two times) to close the mailbox size view again.

Can I Sort Folders by Size?

It's a pity the Folder Size view does not allow you to sort the folder list by size.

Reduce the Size of an Outlook File by Archiving Mail

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

Find the Biggest Emails in Your Outlook Folders

To have Outlook gather all the biggest emails found across all your folders:

  1. Click in the Search Current Mailbox field in your Outlook inbox.
    • You can also press Ctrl-E.
  2. Make sure the Search ribbon is visible and expanded.
  3. Click Search Tools in the Search ribbon's Options section.
  4. Select Advanced Find… from the menu that has appeared.
  5. Make sure Messages is selected under Look.
  6. To search more folders than the inbox (or whichever folder is currently open in Outlook's main window):
    1. Click Browse….
    2. Make sure all the folders you want to search are checked under Folders:.
      • Typically, check the root folder for the account or PST files you want to include in your search and make sure Search subfolders is checked as well.
      • Unfortunately, Outlook will not let you search across accounts and PST files.
    3. Click OK.
  7. Open the More Choices tab.
  8. Make sure greater than is selected under Size (kilobytes).
  9. Enter something like 5000 (~5 MB) under Size (kilobytes).
    • You can choose a bigger or smaller number, of course, to have more or less results returned.
  10. Click Find Now.
  11. To sort the search results by size:
    1. Click By Date in the search result headers.
    2. Select Size from the menu that has appeared.

    Now, double-click any item to open it and deal with it as you see fit. You can also click the red x () in search results to delete any message right away.

    (Updated April 2016, tested with Outlook 2003, 2007, 2010 and Outlook 2016)