Virtualization Ratio Calculator
Measure the three ratios that describe a virtual estate: VMs per host, vCPU per core and allocated versus physical memory.
Inputs
VMs per Host
24.0VMs
vCPU per Physical Core
3.50:1
Allocated to Physical Memory
0.90:1
Average vCPUs per VM
4.67vCPU
Density Score
98/ 100
Estate Assessment
Balanced estate — density, CPU and memory ratios are all in healthy ranges
Step by step
Values used
Hypervisor hosts = 10 hosts; Virtual machines = 240 VMs; Total physical cores = 320 cores; Total vCPUs allocated = 1,120 vCPU; Total physical memory = 5,120 GiB; Total memory allocated to VMs = 4,600 GiB; Target VMs per host = 25 VMs
Virtualization Ratio
VMs per host = VMs ÷ hosts; vCPU per core = allocated vCPUs ÷ physical cores; memory ratio = allocated VM memory ÷ physical memory. The density score weights those 40/30/30 against healthy bands.
VMs per Host
= 24.0 VMs
vCPU per Physical Core
= 3.50 :1
Allocated to Physical Memory
= 0.90 :1
Average vCPUs per VM
= 4.67 vCPU
Density Score
= 98 / 100
Estate Assessment
= Balanced estate — density, CPU and memory ratios are all in healthy ranges
How it works
Three ratios describe an estate and they fail differently. VMs per host is a commercial number, vCPU per core is a scheduling number that only hurts once ready time rises, and the memory ratio is the hard one — above 1.0 the hypervisor is reclaiming, and beyond about 1.4 it is usually swapping. These are the numbers reported to management and used in licence negotiations, and each has a different failure mode — quoting only VMs per host hides whether the estate is one workload spike away from memory contention.
Formula
Virtualization Ratio
VMs per host = VMs ÷ hosts; vCPU per core = allocated vCPUs ÷ physical cores; memory ratio = allocated VM memory ÷ physical memory. The density score weights those 40/30/30 against healthy bands.
- vCPU per core
- Healthy band is roughly 2:1 to 5:1 for general-purpose workloads
- memory ratio
- Above 1.0 means overcommit; above 1.4 usually means active reclamation
- density score
- Composite of density against target plus CPU and memory ratio health
Frequently Asked Questions
How is Virtualization Ratio calculated?
VMs per host = VMs ÷ hosts; vCPU per core = allocated vCPUs ÷ physical cores; memory ratio = allocated VM memory ÷ physical memory. The density score weights those 40/30/30 against healthy bands. Three ratios describe an estate and they fail differently. VMs per host is a commercial number, vCPU per core is a scheduling number that only hurts once ready time rises, and the memory ratio is the hard one — above 1.0 the hypervisor is reclaiming, and beyond about 1.4 it is usually swapping.
Why does Virtualization Ratio matter?
These are the numbers reported to management and used in licence negotiations, and each has a different failure mode — quoting only VMs per host hides whether the estate is one workload spike away from memory contention.
What values do I need to enter?
This calculator takes 7 inputs: Hypervisor hosts, Virtual machines, Total physical cores, Total vCPUs allocated, Total physical memory, Total memory allocated to VMs, Target VMs per host. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.
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