Starting with vSphere 5.0 VMware will introduce vRAM Entitlement. Shortly after the initial intro they also changed the model slightly based on customer and partner feedback.
VMware now released a free tool, called the vSphere Licensing Advisor, which will analyze your existing infrastructure, it works with Virtual Infrastructure 3.5, vSphere 4.0 and vSphere 4 environments. The tool will show you the vRAM capacity you have and the one you need.
Prerequisites: Read more »