How big is your Outlook?


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Find the size of your Outlook data files, then don’t worry about it.

Checking the size of your Outlook data files is pretty easy, you can also find out which folders are taking up space.

In any version of Outlook (we checked Outlook 2010, Outlook 2007 and Outlook 2003) right-click on the top level of the folder tree. That’s the item in folder view that usually displays a dashboard in the main part of the page.

Outlook data file properties menu image from How big is your Outlook? at Office-Watch.com

Choose, ‘Data File Properties’ or ‘Properties for … ‘

On the General tab choose the ‘Folder Size’ button and wait a few moments while Outlook totals everything up.

You’ll see a list of all the folders and sub-folders in that data file with the total size of items contained in it. Here’s a very simple and small example.

Outlook folder sizes image from How big is your Outlook? at Office-Watch.com

If you have an Exchange Server connection there’s two tabs ‘Local Data’ and ‘Server Data’ so you can compare what is stored in the local OST file and the main server storage.

Outlook folders for Exchange Server image from How big is your Outlook? at Office-Watch.com


What, me worry?

If you’re using Outlook 2003 or later with a ‘Office Outlook Personal data file’ (not ‘Outlook 97-2002 format) then you don’t have to worry about your PST file getting too big until it reaches 20GB or more.

Note: Exchange Server users probably have a lower Outlook data limit set by their network administrators.

From Outlook 2003 onwards, the PST file format has a theoretical size limit into the terabyte range. In practice, PST’s should not get larger than



  • 20GB for Outlook 2003/2007
  • 50GB for Outlook 2010

Outlook will warn you before you reach those limits (unlike in the shameful days of Outlook 2002 when it just stopped cold at 2GB).

A PST/OST of 20GB is a rarity even for a heavy email user over a long time. Peter Deegan, Office Watch’s editor-in-chief has ‘his life’ in Outlook with sent and received emails, calendars and more going back more than a decade – his PST is still only 7GB.

The point is … don’t worry about your Outlook file size. For years we’ve received emails with tales of deleting all old messages (regardless of content) and other methods to keep Outlook data trim (like AutoArchive). In many cases, more time is spent deleting and moving messages than might be saved in any small performance benefits.

Deleting Outlook items might have been necessary a decade ago, but not these days. We suggest letting Outlook keep your old emails, sent messages, calendar etc. With search in Outlook 2007/2010 you can easily find items from among thousands of messages. As email becomes a more important part of our lives, those past emails and appointment details can be a surprisingly useful and quickly accessed resource.

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