You can try using the "What-If Analysis" option to forecast workload handling on the clusters in your environment using vROPS. Kindly refer: What-If Analysis - Workload
It would be helpful if you can let us know the vROPS version you are currently using so that we can explore other options for capacity planning as well.
I am using vROPS version 6.5.
What if gives stats if I want to move vm etc. But If I am taking vms out of one cluster and moving to another cluster in same VC. How much capacity we would need.
Could see its there in version 8.0 , how I want it.
Thanks for all your replies.