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Hypervisor Consolidation Calculator

Work out how many hypervisor hosts replace a fleet of physical servers, and the capex and power that consolidation changes.

About Hypervisor Consolidation Calculator

Consolidation works because standalone servers sit almost idle: sizing against measured consumption rather than installed capacity is what produces ratios of 15:1 or better. CPU can then be overcommitted, but memory cannot, so the memory side usually decides the host count while the CPU side decides whether the overcommit ratio is defensible. Consolidation business cases live or die on the ratio, and sizing from installed cores instead of consumed cores understates the ratio by an order of magnitude — while ignoring the memory constraint overstates it. Treat the capex and electricity figures as editable placeholders and substitute your own quotes and tariff.

Formula

Hypervisor Consolidation

hosts = max(consumed cores ÷ (host cores × overcommit × target utilisation), consumed memory ÷ (host RAM × target utilisation × 0.94)), rounded up.

consumed cores
Physical cores × measured utilisation, not installed cores
target utilisation
Utilisation you want the new hosts to run at, leaving headroom
0.94
Roughly 6% of host memory lost to hypervisor overhead

Worked example

With the default values below, Hypervisor Consolidation Calculator returns Hypervisor Hosts Required of 3. Change any input above and every figure here is recalculated in your browser.

Inputs used

Physical servers to consolidateaccepts 1–20,000 servers
60 servers
Cores per physical serveraccepts 1–256 cores
8 cores
Average CPU utilisation todayaccepts 1–100 %
12 %
Memory per physical serveraccepts 1–6,144 GiB
32 GiB
Average memory utilisation todayaccepts 1–100 %
45 %
Cores per new hypervisor hostaccepts 1–512 cores
32 cores
Memory per new hypervisor hostaccepts 8–24,576 GiB
512 GiB
Target utilisation on new hostsaccepts 20–95 %
70 %
vCPU per physical coreaccepts 1–12 ratio
4 ratio
Purchase price per hypervisor hostaccepts 0–1,000,000 USD
18,000 USD
Power draw per physical serveraccepts 10–5,000 W
350 W
Power draw per hypervisor hostaccepts 10–10,000 W
800 W
Electricity priceaccepts 0–5 USD/kWh
0.14 USD/kWh

Results

Hypervisor Hosts Required
3 hosts
Consolidation Ratio
20.0 :1
Hardware Capital Cost
$54,000.00
Annual Electricity Saving
$22,811.04
Power Draw Reduction
88.6%
Sizing Driver
Memory drives the host count — buy larger DIMM configurations, not more sockets

Step by step

  1. 1Values used
  2. 2Hypervisor Consolidation
  3. 3Hypervisor Hosts Required= 3 hosts
  4. 4Consolidation Ratio= 20.0 :1
  5. 5Hardware Capital Cost= 54,000.00
  6. 6Annual Electricity Saving= 22,811.04
  7. 7Power Draw Reduction= 88.6
  8. 8Sizing Driver= Memory drives the host count — buy larger DIMM configurations, not more sockets

Assumptions and limits

  • The result is derived only from the 13 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Hypervisor Consolidation calculated?

hosts = max(consumed cores ÷ (host cores × overcommit × target utilisation), consumed memory ÷ (host RAM × target utilisation × 0.94)), rounded up. Consolidation works because standalone servers sit almost idle: sizing against measured consumption rather than installed capacity is what produces ratios of 15:1 or better. CPU can then be overcommitted, but memory cannot, so the memory side usually decides the host count while the CPU side decides whether the overcommit ratio is defensible.

Why does Hypervisor Consolidation matter?

Consolidation business cases live or die on the ratio, and sizing from installed cores instead of consumed cores understates the ratio by an order of magnitude — while ignoring the memory constraint overstates it. Treat the capex and electricity figures as editable placeholders and substitute your own quotes and tariff.

What values do I need to enter?

This calculator takes 13 inputs: Physical servers to consolidate, Cores per physical server, Average CPU utilisation today, Memory per physical server, Average memory utilisation today, Cores per new hypervisor host, Memory per new hypervisor host, Target utilisation on new hosts, vCPU per physical core, Purchase price per hypervisor host, Power draw per physical server, Power draw per hypervisor host, Electricity price. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

Why size against consumed rather than installed capacity?

A physical server bought for peak load runs at roughly 10% average CPU, so its installed cores are mostly idle capacity you are paying to cool. Virtualisation's whole value is reclaiming that gap, which only appears if you size on measured consumption plus headroom.

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