The Operations Manager-Team has released an interactive Excel-document that can be used for planning and sizing of your System Center Operations Manager 2012 Deployment.
http://blogs.technet.com/b/momteam/archive/2012/04/02/operations-manager-2012-sizing-helper-tool.aspx
You can download the latest version of the Tool from the Download page for System Center 2012 – Operations Manager Component Add – On,
http://www.microsoft.com/en-us/download/details.aspx?id=29270
Or from this direct link:
http://blogs.technet.com/cfs-file.ashx/__key/communityserver-components-postattachments/00-03-48-96-45/System-Center-2012-Operations-Manager-Sizing-Helper-Tool-v1.xls
