How to Increase Outlook PST File Size Limit

Microsoft Outlook stores emails, calendar items, and contacts in a special data file called a PST (Personal Storage Table). By default, each version of Outlook has a size limit for PST files. Once this limit is reached, Outlook may stop saving new emails or show errors like “The Outlook data file has reached the maximum size. To reduce the amount of data in this file, permanently delete some items that you no longer need.”

Default PST Size in Outlook different versions:

Outlook Version	Default PST Size Limit
2003	20 GB
2007	20 GB
2010	50 GB
2013	50 GB
2016	50 GB
2019	50 GB
2021	50 GB

(Note: Microsoft skipped Office 13.0. Also, Outlook 2016, 2019, and Microsoft 365 all use 16.0.)

The good news? You can increase the PST file size limit by tweaking the Windows Registry. Let’s see how.

Step 1: Go to Registry Editor.

1. Search Registry Editor in search bar

2. Go to this path: Computer\HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\PST

Depending on your Outlook version, the registry path will look like this:

Outlook 2003 : HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\PST
Outlook 2007 : HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\PST
Outlook 2010 : HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\PST
Outlook 2013 : HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\PST
Outlook 2016 : HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\PST
Outlook 2019 : HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\PST
Outlook 2021 : HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\PST

Step 2: Create the required DWORD values

1. Inside the PST folder:
2. Right-click on the right panel → New → DWORD (32-bit) Value.
   • 
3. Name it MaxLargeFileSize.
   • This value sets the maximum size limit (in MB) for the PST file.
   • 
4. Again, right-click → New → DWORD (32-bit) Value.
5. Name it WarnLargeFileSize.
   • 

Step 4: Modify the values

1. Double-click MaxLargeFileSize → Select Decimal.
   • Enter a value in MB. Example: 102400 for 100 GB.
   • 
2. Double-click WarnLargeFileSize → Select Decimal.
   • Enter a slightly smaller number than MaxLargeFileSize. Example: 97280 for 95 GB.
   • 

👉 Always keep WarnLargeFileSize at least 1–2 GB less than MaxLargeFileSize.

Step 5: Close Registry Editor

• Close the Registry Editor and restart Outlook for the changes to apply.

⚠️ Important Notes

• Be careful while editing the registry — wrong changes can affect your system.
• Always backup your registry before making changes.
• Increasing PST size too much can slow down Outlook performance. Consider archiving old emails instead of relying on a single huge PST.
• Default Outlook PST size limit is 50 GB (for Outlook 2010 and later).
• You can safely increase it up to 100 GB, but don’t set it too high (huge PST files may slow down Outlook).
• If your PST is already full, you may need to compact the PST after increasing the size.

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