Server Virtualization Calculator

Calculate ESX host requirements for VM workloads

VM Workload

VM Count

vCPU per VM

vCPU

RAM per VM (GB)

ESX Host Specifications

Platform

Host CPU Cores

cores

Host RAM (GB)

Constraints

vCPU-to-Core Ratio

Target CPU Utilization (%)

Target RAM Utilization (%)

N+1 High Availability

How to use Server Virtualization Calculator

1Enter the number of physical servers and their average CPU/RAM utilization today.
2Enter target consolidation ratio and the specs of the new virtual host.
3Read the reduced host count, power savings and rack space freed.

hostsNeeded = ceil(physicalLoad / (hostCap × consolRatio)); savedPower = physicalPower - hostsNeeded × hostPower

Virtualization lets many underused physical servers share fewer, larger hosts, raising utilization from often under 15% to 60–80%.

The biggest wins are fewer units to power and cool, less rack space, and simpler hardware lifecycle management.

What consolidation ratio is realistic?

Ratios of 10:1 to 20:1 are common for general workloads, less for latency-sensitive ones.

Does virtualization always cut power?

Yes on total facility power, though each host draws more than the old servers it replaces.

What about licensing?

Hypervisor and guest OS licenses can offset savings, so model them before committing.

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