With new versions of vSphere, VMware has reduced memory overhead based on CPU and RAM you assigned to VM. Attached is the Memory overhead calculator, this will not give you exact size as it is a bit old but will give you overview.
To find exact amount of overhead on each VM, please see the log in VM log file :
"In order to find out how much overhead memory is needed for your specific configuration, first power on the virtual machine in question. Look in the vmware.log file. When the virtual machine powers on, the amount of overhead memory it needs is printed to the log. Search within the log for VMMEMto see the initial and precise amount of overhead memory reserved for the virtual machine."