If you use Microsoft Outlook to manage large volumes of email, you may eventually run into the dreaded “Outlook data file has reached its maximum size” error. By default, Outlook limits .pst (and .ost) files to 50 GB — but with a simple registry tweak, you can safely raise that limit.
This step-by-step guide shows you how to increase the maximum PST file size in Outlook 2010, 2013, 2016, 2019, 2021, and Microsoft 365 for Windows.
Default Outlook PST limits by version
|
Outlook Version |
Default Max Size |
Max You Can Set via Registry |
|
Outlook 2010 or later |
50 GB |
~100–150 GB (recommended) |
|
Outlook 2003 / 2007 |
20 GB |
~50 GB (max recommended) |
|
Outlook 2002 or older |
2 GB |
Cannot increase |
How to increase Outlook PST file size (Step-by-Step)
1. Open the Registry Editor
- Press Windows + R to open the Run dialog.
- Type: regedit and hit Enter.
- Click Yes if prompted by User Account Control (UAC).
2. Navigate to the PST registry path
Find the path based on your Outlook version:
|
Outlook Version |
Registry Path |
|
2016 / 2019 / 2021 / 365 |
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\PST |
|
2013 |
...Office\15.0\Outlook\PST |
|
2010 |
...Office\14.0\Outlook\PST |
|
2007 |
...Office\12.0\Outlook\PST |
Tip: You can paste the full path into the Registry Editor's address bar.
3. Create or edit registry values
Once inside the PST key:
- Right-click the right panel → New > DWORD (32-bit) Value
- Create or edit these two values:
MaxLargeFileSize
- Description: Maximum allowed size for PST files.
- Value: Set in MB (e.g. 102400 for 100 GB).
- Type: DWORD (32-bit)
WarnLargeFileSize
- Description: Triggers a warning before the max is reached.
- Value: A bit smaller than the max, e.g. 95000.
- Type: DWORD (32-bit)
To edit a value: Double-click it → select Decimal → enter the number in MB.
4. Close and restart Outlook
Once changes are made:
- Close the Registry Editor.
- Restart Outlook (and ideally your PC) to apply changes.
Example: raise PST limit to 100 GB
|
Registry Value |
Type |
Value (Decimal) |
Effect |
|
MaxLargeFileSize |
DWORD (32-bit) |
102400 |
Sets max at 100 GB |
|
WarnLargeFileSize |
DWORD (32-bit) |
95000 |
Warns at 95 GB |