VMware has launched an online service that it claims can help users evaluate the true costs of server virtualisation expenses.

The VMware Cost-Per-Application Calculator enables users to estimate cost-savings from VMware software - and compare that to other virtualisation wares from competing vendors, such as Microsoft.

Virtualisation calculators are not entirely new, of course. Microsoft has a virtualisation RoI calculator. Parallels has one for desktop virtualisation, too. But VMware is taking a new approach.

The company explained in a statement that looking at "cost per application" as a metric, rather than license pricing, considers the number of virtual machines that can be run on each hardware server -- a rate VMware dubbed the "virtual machine density."

The higher the virtual machine density, the more an IT shop can cut costs including hardware, networking, storage, power and cooling, and datacentre space, the company claimed.

"End users should look to cost per application to streamline and simplify their assessment of the total acquisition costs of a server virtualisation environment," industry analyst firm Taneja Group said in a report.