How to Increase PST File Size in Outlook? Use Free Solution

  

Rollins Duke   
Published: September 3rd, 2025 • 9 Min Read

Several business professionals want to increase the PST file size in Outlook 2021, 2019, 2016, 2013, 2010, 2007, and 2003 editions because they are receiving an error message. If you see a pop-up message like The Outlook data file PST has reached the maximum size. To reduce PST file size, permanently delete items that are no longer needed.

The size of files is always a key concern, and it’s no different when it comes to OST and PST files in Outlook. If the user is an Outlook user, they have likely encountered issues related to file sizes. This is a problem that affects many Outlook users. We often share a large number of emails and attachments every day, surpassing our PST size limit. In this article, we will explore Outlook PST file storage in detail and learn how to increase the PST file size limit.

Recommended Size of PST File by Microsoft

All versions of Microsoft Outlook, including Outlook 2021, 2019, 2016, 2013, 2010, 2007, 2003, and 2002, support ANSI and UNICODE personal folders (.PST) files. However, the maximum size limit for non-UNICODE PST files is 2 GB across all Outlook versions. On the other hand, the maximum size limit for UNICODE PST files varies, depending on the Outlook version. Before we dive into increasing the PST file size, let’s take a look at the PST size limits for different Outlook versions:

Read these tables to understand the maximum recommended size of PST file by Microsoft.

Outlook for 2010, 2013, 2016, 2019, and 2021

Outlook for 2003 and 2007

Consequences of Oversized PST Files

When the size of the PST files increases beyond the set limit, it adversely affects the performance of the entire Outlook. Here are some of the common reasons why users face such issues:

• A PST file with an enormous size can cause a halt in Outlook due to the files taking more time to load, stalling in receiving/sending emails, and showing “Not responding” pop-ups frequently.
• Another effect of Outlook containing an oversized PST file it opens the risks to have corruption of the information, which can cause temporary or permanent loss of of essential emails and data.
• Proves to be ineffective and inefficient to back up or search through emails in large PST since it can be time-consuming.
• Users tend to experience unforeseen crashes due to Outlook dealing with PST files that are extremely large.

Neglecting extremely large PST files can have a detrimental impact on Outlook operation, and it may even lead to numerous losses as mentioned above. To avoid such outcomes, it is crucial to be aware of the default size limitations for PST files and find ways to maximize their size. With the assistance of adding and modifying registry entries, it is possible to set the maximum PST file size limit.

Registry Entries to Increase PST Size in Outlook

Now that the users have gained enough knowledge about about the size limits in Outlook versions, let’s explore how they can increase the PST file size limit. You have the option to modify the default maximum size of a PST file by editing the registry entries. Here are four registry entries that can be adjusted to limit the size of Microsoft Outlook:

• MaxLargeFileSize: This entry limits the extent to which the PST file can grow. Once the file reaches its maximum size, Outlook will prevent it from expanding further.
• MaxFileSize: Like MaxLargeFileSize, this registry entry applies to the ANSI (American National Standards Institute) PST file format.
• WarnLargeFileSize: This entry sets the maximum data size for the PST file. When the data reaches this limit, you cannot add more data.
• WarnFileSize: Similar to WarnLargeFileSize, this registry entry applies to the ANSI PST file format.

How to Increase PST File Size in Outlook Using Regedit

Follow the steps below to manually increase PST size in Outlook using the registry entries:

1. In the first step, press Win+R on the screen. Type “regedit” and click “OK“.
   
2. Find the “Registry Editor” and navigate to HKEY_CURRENT_USER.
   
3. Afterwards, expand the file and go to Software > Policies > Microsoft > Office > Outlook > PST.
   
4. Under PST, users will find several options (MaxFileSize, WarnFileSize, MaxLargeFileSize, WarnLargeFileSize). Right-click on the entry associated with your Outlook account.
   
5. Select “Modify” and enter the desired value in the Value Data Box. Click “OK“.
   

Note: It is to be kept in mind that if the registry value hasn’t been added already, the user will need to configure it by going to PST > New > DWORD Value.

Considerations Before Users Increase PST Size in Outlook

Utilizing manual methods is effective to increase PST size in Outlook. However, it can only be done through best practices that are possible only by the technical experts to avoid any kind of issue such as data loss, file corruption, etc. Here we have described some important points that you need to consider before starting the manual method:

• Possibility of Errors or Data Loss: Using traditional techniques to increase PST size in Outlook requires technical expertise and accuracy. Therefore, making a mistake when entering these values can cause problems.
• PST File Corruption: It is essential to maintain at least a 5% difference between the Warn Large File Size and Max Large File Size. Otherwise, the oversized files can lead to PST file corruption and permanent loss of data.
• Outlook Performance Issues: This method can significantly decrease the performance of a user’s Outlook application, resulting in it being stuck processing, sudden crashes or not responding.
• User Expectations: Manual techniques do not guarantee breaking PST files according to the user’s expectations.
• Issues in Compatibility: Since different versions of Outlook have different size limits, users tend to get puzzled while modifying their current version’s settings.
• No Assurance of Safety: Exceeding the size of the PST files does not at all safeguard them against damage or corruption.

Advantages of the Recommended Software

• Prevents file corruption by dividing oversized files into multiple small parts.
• Provides multiple filters for dividing large PST files.
• Allows you to set the size for resultant PST files (e.g., 2 GB, 5 GB, 10 GB, and 20 GB).
• Supports both ANSI and Unicode PST files.
• Users can easily split their files according to date, size, folder, year, email address, and many more filters to make sure users can the flexibility.
• This robust software is perfectly fits with all versions of Outlook from 2003 to 365 including both ANSI and UNICODE formats.
• Users can stop stressing about the information hierarchy as the software makes sure every element in an email is sustained, aligned, and present during the splitting process.
• Offers a user-friendly interface, making it accessible to both individuals and professionals with or without technical expertise.
• Removes the manual technique of registry and provides stable performance of the generated PST files.

Conclusion

Managing the size of PST files in Outlook is considered to be an essential task to ensure smooth workflow and prevent file corruption. While manual methods involving registry entries can be effective to increase PST file size in Outlook, they require technical expertise and come with potential risks.

For users who do not grasp technical knowledge or wish to minimize such complications, using a reliable file splitter application is recommended. By splitting large PST file into smaller files, and manageable parts, users can increase their file size without compromising performance or risking file corruption.

Instead of stressing about “How do I increase the size of my PST file in Outlook 365?” effectively adjust the Outlook data information using a trusted software tool like the PST splitter that ensures safety, security, and efficiency of the data information.