When an Outlook 2010 or 2007 user tries to open more than 30 calendars simultaneously they may receive the following error.

Outlook 2010 error when opening more than 30 calendars
Outlook 2010 error when opening more than 30 calendars

You cannot view more than 30 calendars at once. To view this calendar, clear the check box for one of the calendars.

Your first instinct might be to check the Exchange 2010 throttling policies, however this behaviour is controlled by a registry setting on the client computer.

Open Regedit and navigate to HKEY_CURRENT_USERSoftwarePoliciesMicrosoftOffice14.0OutlookOptionsCalendar

Edit or create a DWORD entry of CalendarMaximumNumber and set the desired decimal value.  The value must be between 10 and 100 and also must be a multiple of 10 (eg 40, 50, 60, and so on).

This limit is actually mentioned in the Office online documentation for Outlook 2007.

About viewing multiple calendars

You can open a second calendar in a new window and display up to 30 calendars in side-by-side view.

About the Author

Paul Cunningham

Paul is a former Microsoft MVP for Office Apps and Services. He works as a consultant, writer, and trainer specializing in Office 365 and Exchange Server. Paul no longer writes for Practical365.com.


  1. Phillip Mathews

    Paul, we are having this same issue with 2013. My boss changed his registry keys just like you have above and it works great for him. We do have a few users that have this issue but when we go to the keys it stops at Microsoft, it does not contain the office folder at all. I have been doing quite a bit of Google searching on this issue and no one seems to have a fix out there.

    Do you know if there is a fix for this issue?

    Thanks for your time.


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