VM Storage Calculator
Calculate vSphere ESX cluster storage capacity requirements
How to use VM Storage Calculator
- 1Enter the number of VMs, average disk size per VM, and the RAID/erasure overhead factor.
- 2Enter growth rate and snapshot retention you plan to keep.
- 3Read the total raw and usable capacity required before provisioning storage.
Sizing storage for virtual machines
usable = VMs × diskGB × (1 + overhead); raw = usable / raidEfficiencyVirtual environments need overhead for snapshots, replicas and RAID parity, so usable capacity is always less than raw disks.
Plan for at least 20–30% free headroom so live migration and patching never stall when a datastore fills up.
Frequently asked questions
Why is usable less than raw?
RAID parity, erasure coding and snapshots consume capacity before any guest data is stored.
How much headroom should I keep?
Aim for 20–30% free to absorb spikes, snapshots and maintenance operations.
Do thin provisioned disks save space?
They delay usage but the total logical size still must fit the datastore when fully written.
More Tools
VM Storage Calculator
Calculate vSphere ESX cluster storage capacity requirements
Kubernetes Capacity Calculator
Calculate Kubernetes cluster node requirements for your workload
Server Virtualization Calculator
Calculate ESX host requirements for VM workloads
VMware Licensing Calculator
Calculate VMware VCF/VVF licensing costs