Windows Server and SQL Server cluster licensing calculator

There are three compliant patterns. License every host with Datacenter, which covers unlimited VMs wherever they move. License every host with enough Standard licences for the most Windows VMs it could ever run at once, including after a failure. Or, with Software Assurance or subscriptions, license each VM by its virtual cores (at least 8 per VM, 16 in total) so the licences move with the VMs within a server farm. Every physical-core licence has the 8-per-processor and 16-per-server minimums.

No. Licences assigned by physical core belong to the server and can be reassigned no more than once every 90 days, except after permanent hardware failure. Each host must already be licensed for the VMs that could run on it. That is why Microsoft’s guidance says Datacenter gives the most flexibility for moving VMs, and why Standard must be sized for each host’s peak.

No. Microsoft’s Product Terms make licensing by virtual OSE available only for subscription licences or licences with active Software Assurance. Several forum answers tell customers without SA to “license each VM for 4 or 8 cores”; that is not a compliant route.

License every physical core of every host the SQL VMs can run on with Enterprise; each host may then run one SQL Server OSE per licence assigned to it, and extra licences add extra OSEs. Enterprise core licences also cover Standard VMs through the down-edition right, whereas Standard core licences on a host cover only its physical operating system. For Standard you can instead use Server + CAL: one Server licence per VM, and because a licence without SA can move at most every 90 days, a VM that can run on several hosts needs a Server licence on each of them. Per-VM core licensing is not available without SA.

Only with Software Assurance or a subscription (and with Azure Arc pay-as-you-go). Then each licensed OSE gets one passive copy for any purpose including high availability, plus two passive disaster-recovery copies, one on any server and one in Azure, which must be asynchronous with manual fail-over. Passive copies may not serve data or run active workloads. With Server + CAL the CALs need SA too. Without SA there are no fail-over rights, so Always On secondaries and fail-over cluster nodes are licensed like active servers.

The counting rules are the same as SQL Server 2022: every physical core with 4 per processor, or every virtual core with 4 per VM (SA or subscription only). SQL Server 2025 Standard can now use up to the lesser of 4 sockets or 32 cores, up from 24, with a 256 GB buffer pool. Microsoft’s US list prices are unchanged: $15,123 for an Enterprise 2-core pack and $3,945 for Standard.

It costs $0.046 per core-hour (£0.0339), about $33.58 per core per month. Each VM pays for its own cores: a pay-as-you-go host gives its VMs no rights, and billing continues while a machine is switched off. For comparison, Datacenter for a 2 × 16-core host lists at $13,542 and covers unlimited VMs, which pay-as-you-go matches after about 403 VM core-months. It suits short-lived or small workloads better than dense clusters.

Microsoft publishes no rule saying they do. Its guidance says to license each server for its peak and that VMs may move freely as long as usage never exceeds what each server is licensed for. If your placement rules genuinely cap how many Windows VMs a host can run, and you can show they are enforced, that cap is your peak. The calculator defaults to the worst case and labels any lower figure as your declaration.

A single data centre, or two data centres in time zones no more than four hours apart, or both within the EU or EFTA. Per-VM licences can move with VMs between hosts in the same server farm as often as needed, but between server farms no more than once every 90 days.