Calculating Resource Needs for Switching to Multitenant Container databases

With our look towards Oracle 12c we are trying to determine if the cost of the Multitenant option is justifiable.  I'm unsure how to go about calculating that.  In theory if we make all of our databases pluggable and perhaps have only one or two container databases we drastically reduce the horsepower our RAC would need in terms of both memory and CPUs.  There's also some human resource savings by making upgrades/patches and general maintenance a bit more streamlined and less time consuming.

On the hardware resource side are there any guidelines or tools available to help in calculating current usage and determining the hardware needs for a multitenant environment?  I was thinking we should be able to pull out average and maximum CPU, memory utilizations, various memory sizes and usages of each database, existing hardware, etc.  Somehow do some calculations on those and at the end get a good idea of how much less hardware would be required for the same loads within a multitenant environment.  So far my googling and searching Oracle support hasn't found such tools or calculation guidelines.