Memory and core for Host server

Hello all

We configured one Windows 2012 Datacenter core with 64 GB RAM and teh server has 12 cores (2 CPU X 6 core). Four virtual servers are required to be configured with 3 cores & 16 GB of RAM for each (dedicated cores and memory for each Virtual server). For the host server how much memory & core is required, how we can calclulate the requirements

Thanks in advance 

LMS