Do Outlook PST Files Have a Size Limit?

All Outlook versions use PST (Personal Folder) files to store emails, contacts, calendar data and more. There are two kinds of PST files, however.

Outlook 2003 and later use a PST file format capable of storing Unicode (a standard that can represent most alphabets on computers) data that has no theoretical size limit but a practical limit of 20 GB.

Outlook versions before that (97 to 2002) use a PST file format restricted to U.S. English (foreign-language characters need to be encoded in that format) that has a hard-wired limit of 2 GB.

Outlook PST File Size Limits

Here, again, are the two formats, their limits and typical use:

Outlook 97-2002 Personal Folders File (PST)

• Used by:
  • Outlook 97, Outlook 98, Outlook 2000, Outlook 2002
  • IMAP and Windows Live Hotmail accounts in Outlook 2003
  • Outlook 2007 if explicitly chosen
• Size limit:
  • 2 GB
  • Cannot be increased

Outlook 2003-2007 Personal Folders File (PST)

• Used by:
  • Outlook 2003 (with the exceptions above)
  • Outlook 2007
• Size limit:
  • Configurable; 20 GB by default
  • For performance and stability reasons, it is not recommended to increase the limit beyond 20 GB.

As your PST file approaches the limit or suggested maximum size (check the size via the Total size given in the Folder Size dialog), you can move old messages to a separate archive PST file — or delete them, of course.