Increase PST File Size to 100GB: Complete Registry Guide

Increasing the PST file size limit is possible by modifying the Windows Registry, but it should only be done when absolutely necessary. While Microsoft Outlook supports larger PST files in modern versions, simply increasing the limit does not improve performance. In fact, oversized PST files can become slower, harder to manage, and more vulnerable to corruption. If your mailbox keeps growing, there are safer alternatives than allowing a single PST to become excessively large.

Why Do Users Increase PST File Size to 100GB?

Many Outlook users reach the default PST limit because they:

• Store emails for several years.
• Archive multiple mailboxes into one PST.
• Save large attachments locally.
• Need to retain business communications for compliance.
• Want to avoid creating multiple archive files.

As the mailbox grows, users often search for ways to increase Outlook data file size to 100GB instead of splitting or archiving their data.

Side Effects of Increasing the PST Size

Before modifying Outlook's storage limit, consider these drawbacks:

• Outlook may become slower when opening or searching emails.
• Backup and restore operations take significantly longer.
• Large PST files have a higher risk of corruption if interrupted.
• Recovery from a damaged file becomes more difficult.
• File transfers between systems require more storage and time.

For these reasons, Microsoft generally recommends keeping PST files at a manageable size rather than maximizing the storage limit.

How to Increase PST File Size to 100GB

You can increase PST file size to 100GB registry by editing the Windows Registry.

1. Close Microsoft Outlook.
2. Press Windows + R, type regedit, and press Enter.
3. Navigate to the Outlook registry location according to your Outlook version.
4. Locate or create the following DWORD values:
   • MaxLargeFileSize
   • WarnLargeFileSize
5. Set the values in MB.
   • MaxLargeFileSize = 102400 (100 GB)
   • WarnLargeFileSize = around 97280 (95 GB)
6. Save the changes.
7. Restart Outlook.

After applying these settings, Outlook can use the updated storage threshold.

Can You Increase PST File Size to 200GB?

Technically, users may search for increase PST file size to 200GB, but doing so is generally not recommended. Extremely large PST files often experience performance degradation and are more likely to become unstable. Even if registry values are modified beyond 100GB, Outlook performance and long-term reliability can suffer.

How to Make PST File Larger Than 50GB

Modern Outlook versions have a default PST limit of approximately 50GB. If you need to make PST file larger than 50GB, editing the registry is the supported method. However, this should be considered only when there is a genuine business requirement and adequate backup procedures are in place.

A Better Alternative

Instead of continuously increasing storage limits, many administrators prefer dividing large Outlook data files into smaller, organized PSTs. This keeps Outlook responsive while reducing the chances of corruption.

The SysTools PST File Splitter offers an easier approach to split PST file without Outlook based on size, date, year, folder, or email ID without affecting mailbox data. This allows users to manage growing Outlook archives without relying on registry modifications or maintaining a single massive PST.

Conclusion

Although you can increase PST size to 100GB through registry changes, doing so should be approached carefully because larger PST files can impact Outlook's stability and performance. For users dealing with continuously expanding mailboxes, maintaining smaller PST files is often a safer and more practical long-term solution than repeatedly increasing storage limits.