Understand the licenses.
See how they add up.
Windows Server runs the operating system. SQL Server runs the database. Learn what to license, what to count, and where the two meet.
Jump to minimum core licenses by scenario
Examples you can change
Minimum core licenses, by scenario.
Start with the minimum. Then license the actual core count if it is higher.
These are core licenses, not packs. One two-core pack contains two core licenses. Windows Server and SQL Server are counted separately.
| Your scenario | Minimum core licenses | How to apply it |
|---|---|---|
| Windows Server Standard Physical host | 16 per server 8 per processor | License all physical cores, applying both minimums. Each full host set grants 2 OSEs; repeat the full set for each additional 2. |
| Windows Server Datacenter Physical host | 16 per server 8 per processor | License all physical cores, applying both minimums. One full host set grants unlimited Windows Server OSEs on that host. |
| Windows Server Standard or Datacenter Individual VM | 8 per VM | License all virtual cores in each VM, with a floor of 8. Qualifying server and CAL coverage required. The disputed 16-core customer minimum is separate—see the note below. |
| SQL Server Standard or Enterprise Physical-core route | 4 per processor | License all physical cores, with a floor of 4 for each processor. There is no Windows-style 16-core server minimum for SQL. Virtualization rights differ by edition and coverage. |
| SQL Server Standard or Enterprise Individual VM, Per Core | 4 per VM | License all virtual cores, with a floor of 4 per VM; additional mapped hardware threads count. Active SA or a qualifying subscription required. |
| SQL Server Standard Server + CAL | No core minimum under this model | License each OSE with a server license and each accessing user/device with a SQL CAL. This is not free licensing; edition capacity limits still apply. |
Windows Server per-VM customer minimum: Microsoft’s HTML guide also states 16 core licenses per customer, while the downloadable guide and current MCA per-VM clause omit that floor. The VM minimum is 8; confirm the customer-level requirement for your agreement. See the explanation and both calculation scenarios.
Access rights are additional: Windows Server CALs, RDS CALs where applicable, and SQL CALs under Server + CAL. A core minimum does not include these.
Sources: Windows Server Product Terms · SQL Server Product Terms
Start with the layers.
A server can run both products. Each product answers a different licensing question.
Think of licensing as two questions: what may run, and who may access it? A server or core license covers running software. A CAL grants access to a particular server product; it does not install that product.
- Physical core
- A processing core inside a physical CPU. Count cores, not just CPU sockets.
- Virtual core / vCPU
- Processor capacity assigned to a virtual machine. It is not automatically the same as a physical core.
- Virtual machine (VM)
- A software-defined computer running on a host. Several VMs can share one physical server.
- Operating system environment (OSE)
- A physical or virtual environment in which an operating system runs. The term appears throughout Microsoft licensing rules.
- Instance
- A running copy of software. Several SQL instances can run inside one OSE; an instance is not a core or a VM.
- CAL
- Client Access License. Usually assigned to a user or device, rather than counted by simultaneous connections.
Activating software is a technical step. A successful activation does not prove that all core licenses, access licenses, or deployment rights are in place.
Read the rule: Universal software terms
Check your understanding
Read the answer and explanation
No, assess each product separately. The database and operating system are separate licensing layers.
License Windows Server.
First cover the computing capacity. Then check access rights.
One host, two main editions
| Rule | Standard | Datacenter |
|---|---|---|
| Core minimums | All physical cores; at least 8 per processor and 16 per server. | |
| Windows Server OSE rights | 2 OSEs per complete set of host core licenses. | Unlimited OSEs on that licensed host. |
| More VMs | Assign another complete set of host core licenses for each additional 2 OSEs. | No extra core sets for additional Windows Server VMs on that host. |
| Access licenses | Windows Server CALs or other eligible access rights remain necessary, subject to exceptions. | |
If a Standard host runs only virtualization and VM management, its physical Windows Server instance can run in addition to the two permitted virtual OSEs. If the host also runs an application, that physical OSE consumes one of the two rights.
Read the rule: Windows Server 2025 licensing guidance · Windows Server Product Terms · MCA
Try it: cover a physical host
Change the host and VM counts. Watch Standard stack complete license sets.
Minimum: 16 core licenses per host, and 8 per processor. Cover all actual physical cores if higher. Standard stacking repeats the complete host count.
Illustrative single host, identical CPUs, Windows Server guests, no container or cluster calculation. A host used only for virtualization/management does not consume the Standard VM allowance. CALs are additional. Results show license counts, not prices.
Windows Server VMs: two ways to license them
Route 1 — license the host: count its physical cores, then use Standard’s two-OSE allowance per complete set or Datacenter’s unlimited OSE allowance. Route 2 — license individual VMs: with qualifying coverage, count each VM’s virtual cores instead. The physical-host calculator above illustrates Route 1.
With eligible subscription licenses or active Software Assurance (SA), individual Windows Server VMs can be licensed by virtual core: at least 8 core licenses per VM. Both editions cover one virtual OSE under this route; Datacenter does not give unlimited VMs when licensed per VM. CALs used for this route also need qualifying subscription or SA coverage.
The Windows Server HTML guidance states a 16-core minimum per customer for per-VM licensing. The current downloadable guide and MCA product-specific per-VM clause list the 8-core VM minimum without that customer minimum. Confirm the applicable agreement before ordering a small per-VM deployment. The physical-host calculator is unaffected. The individual-VM calculator below shows the guest subtotal and the customer-minimum scenario separately.
Read the rule: Windows Server 2025 licensing guidance · Windows Server Product Terms · MCA
The hypervisor does not replace guest licenses. Windows Server guests still need appropriate rights whether they run on Hyper-V, VMware, or another supported hypervisor. Under the individual-VM route, licensing the guests does not grant the right to run Windows Server in the physical host OSE. Assess any Windows Server host separately.
Standard per VM
License at least 8 virtual cores for each VM. Each licensed VM receives one virtual OSE right—not two. The two-OSE allowance belongs to the physical-host route.
Datacenter per VM
The same 8-core minimum and one virtual OSE right apply. Unlimited VM rights belong to fully licensing the physical host with Datacenter.
| VMs to cover | Calculation | VM core subtotal |
|---|---|---|
| 2 VMs, 4 vCores each | 8 + 8 | 16 core licenses |
| 3 VMs, 8 vCores each | 8 + 8 + 8 | 24 core licenses |
| 1 VM with 4 vCores, 1 with 12 | 8 + 12 | 20 core licenses |
| 1 VM with 4 vCores | 8 for the VM | 8 before resolving the customer minimum noted above; 16 if that minimum applies and no other eligible licenses count. |
Try it: license Windows Server by VM
Calculate the guest core subtotal. The result also shows the 16-core customer-minimum scenario because Microsoft’s sources differ.
Minimum: 8 core licenses per VM. Cover all assigned virtual cores if higher. The separate customer-minimum scenario is shown in the result.
Identical VM sizes; conventional VMs, no containers or cluster design. This is a guest-core calculation, not a purchase recommendation. The customer-minimum scenario assumes no other qualifying core licenses count toward that minimum. For mixed sizes, calculate each VM separately and add its minimum-adjusted cores.
Moving a VM: qualifying individual-VM licenses can be reassigned within the same licensing-defined server farm as often as needed. Moving between server farms is subject to the 90-day restriction. These rights do not permit one set of licenses to run simultaneous copies on two hosts.
Read the rule: Windows Server Product Terms · individual virtual OSE licensing · Windows Server 2025 guidance · virtualization rights
Choose CALs around how people work
User CAL
One named person, using multiple devices. Example: 20 employees each using a laptop and phone → 20 User CALs.
Device CAL
One device, used by multiple people. Example: 30 shift workers using 10 shared terminals only → 10 Device CALs.
The same properly versioned CAL can cover access to multiple licensed Windows Servers in your organization. A 2025 CAL supports 2025 and earlier server versions; an older CAL does not automatically cover a newer server.
Remote Desktop Services adds another layer: users or devices accessing hosted desktops or applications generally need an RDS CAL as well as the base Windows Server CAL. The limited administration exception is not a license for employees to use business applications.
Exceptions and external users
Defined exceptions include certain web/HPC workloads, access from another licensed server, and limited administration. Eligible external users may be covered by individual CALs or an External Connector assigned to each accessed server. An External Connector is not a substitute for employee CALs. Check exact definitions and additive RDS rights in the terms.
Read the rule: Remote Desktop Services CALs · Windows Server Product Terms · MCA
Check your understanding
Read the answer and explanation
32 core licenses. Each complete 16-core set grants two virtual OSEs in this scenario. Four VMs need two sets.
Choose a SQL licensing model.
Edition controls capabilities. The licensing model controls what you count.
| Model | Available editions | What you count |
|---|---|---|
| Per Core | Standard or Enterprise | Physical cores or eligible individual VM cores. No SQL CALs needed. |
| Server + CAL | Standard for new purchases | A server license for each OSE, plus a SQL CAL for every accessing user or device, including indirect access. |
Under SQL Standard’s product-specific terms, one server license permits multiple SQL instances within one physical or virtual OSE. Two SQL VMs therefore need two server licenses, even when they share a host. Properly versioned SQL CALs can access multiple licensed SQL Servers. Existing Enterprise Server/CAL agreements have legacy rules; this guide does not model them.
Source clarification: the general SQL guide describes one running instance under Server + CAL. The MCA product-specific “Running Instances for Standard Edition” clause explicitly permits any number in the one licensed OSE; that clause is used here.
Read the rule: SQL Server Product Terms · MCA · SQL Server 2025 licensing guidance
Count the right cores
License the physical server
License every physical core, with at least 4 core licenses per processor. Standard covers SQL in the physical OSE. Enterprise has additional virtualization rights.
License an individual VM
For SQL Server 2025 Per Core, active SA or a qualifying subscription is required. Count virtual cores, at least 4 per VM. Additional mapped hardware threads must also be licensed.
Enterprise’s unlimited virtualization benefit requires the whole physical host to be licensed with Enterprise core licenses and qualifying SA/subscription coverage. Without that benefit, physically licensed Enterprise has a bounded OSE allowance; it is not automatically unlimited.
Read the rule: SQL Server Product Terms · MCA
Try it: license SQL by VM
See why a small database VM still has a four-core minimum.
Minimum: 4 SQL core licenses per VM. Cover all assigned virtual cores if higher. Active SA or a qualifying subscription is required.
Identical VM sizes, one hardware thread per virtual core, no containers. Standard is limited to 32 cores/threads per VM; this example rejects higher values. Windows Server licensing and access rights are separate.
A connection pool does not shrink your user count
In this illustrative employee-only scenario, 50 SQL User CALs are needed, not one for the application’s shared login. Multiplexing changes the connection path, not the number of people or devices requiring access rights.
Read the rule: Universal software terms · SQL Server 2025 licensing guidance
Free editions have boundaries
Developer: the 2025 Standard Developer and Enterprise Developer editions are for development, testing, and demonstration—not production. Express: can serve small production applications within its license and technical limits; SQL Server 2025 increases the relational database size limit to 50 GB per database. Evaluation: a time-limited evaluation, not an ongoing production license.
Read the rule: SQL Server 2025 editions and limits
Check your understanding
Read the answer and explanation
50. Indirect access still counts. A shared application login does not remove CAL requirements.
Put the two products together.
A worked example: one small business application, with clearly stated assumptions.
Assume one physical server with 16 cores, a Windows Server host used only to manage VMs, two Windows Server VMs, and 20 employees who each access both VMs. SQL Standard runs in one VM. No RDS, external users, or failover servers.
One physical host · 16 physical cores
| Layer | Example requirement | Why |
|---|---|---|
| Windows Server | 16 Standard core licenses | One full host set covers the two VMs; host only manages them. |
| Windows access | 20 Windows Server User CALs | Each employee accesses Windows Server services. |
| SQL Server | 1 SQL Standard server license | SQL runs in one OSE. |
| SQL access | 20 SQL User CALs | All 20 employees access the database, including through the app. |
Alternative: license that SQL VM by core, with eligible SA/subscription coverage and the VM minimum. That removes the SQL CAL requirement, but leaves Windows Server core and access requirements in place. It is a licensing alternative, not a price recommendation.
SQL can also run on Linux. In that case there is no Windows Server OS layer for that SQL VM; assess the actual operating system and all other accessed services.
Read the rule: Windows Server 2025 licensing guidance · SQL Server Product Terms · MCA
Check your understanding
Read the answer and explanation
SQL CALs for that Per Core deployment. Per Core removes SQL CALs. It does not remove the separate operating system licensing requirements.
Know when the answer changes.
Keep the basic model. Recheck these conditions before changing the deployment.
Perpetual licenses, subscriptions & Software Assurance
A perpetual license normally continues to permit the version you acquired after its purchase is paid for. A subscription grants use during its term. SA adds benefits to eligible licenses for a coverage period, including new-version and certain deployment rights. A perpetual license does not keep every SA benefit after SA expires.
Record the product, version, purchasing program, acquisition date, and SA/subscription dates. OEM and retail terms can differ from commercial licensing, particularly for transfer and hardware association.
Read the rule: Software Assurance benefits · Universal software terms
High availability & disaster recovery
“Passive” does not simply mean “a second server.” For qualifying SQL workloads, current terms provide one failover OSE for purposes including HA, plus two DR OSEs: one on eligible servers and one in Azure. Coverage, location, capacity, passive-use and testing conditions apply; CALs also need qualifying coverage under Server + CAL.
A secondary serving reports or other active workloads needs its own licensing. Permitted maintenance such as backups and consistency checks is specifically defined. DR failover OSEs must be asynchronous and manual, and permitted brief DR tests occur every 90 days. License Mobility through SA has different failover provisions.
Windows Server has its own conditional DR rights. Do not assume SQL’s passive rights cover the operating system. Check the separate backup-instance rules, permitted test periods, SA coverage, and host use.
Read the rule: SQL Server Product Terms · MCA · Software Assurance benefits
Moving VMs and clustered hosts
Live migration is a technical capability, not automatic permission to move licenses. Physical Windows Server licensing must cover every destination host for its possible Windows workload. Qualifying per-VM rights allow reassignment within the same server farm; cross-farm reassignment is generally subject to a 90-day limit.
SQL mobility also depends on the model and qualifying coverage. General license reassignment has a 90-day restriction with defined exceptions. Document all possible destinations and maximum workloads after a host failure.
Read the rule: Universal software terms · Windows Server Product Terms · MCA · SQL Server Product Terms · MCA
Azure, Azure Arc & outsourced hosting
Azure Hybrid Benefit can apply eligible existing licenses to supported Azure services; Windows and SQL have different eligibility and conversion rules. Azure Arc also offers pay-as-you-go licensing options. Connecting a server to Arc alone does not buy a license.
Running software on a hosting provider’s infrastructure introduces provider eligibility and outsourcing conditions. Check the Flexible Virtualization Benefit, Authorized Outsourcer definitions, and applicable License Mobility rules before carrying an on-premises calculation into a hosted environment.
Read the rule: Windows Server 2025 licensing guidance · SQL Server 2025 licensing guidance · Software Assurance benefits
Older versions, CAL versions & containers
Downgrade rights can allow earlier software versions, subject to the license and agreement. They do not mean that every rule from an old guide applies to a newer purchase. Match CAL versions to the server version being accessed.
Containers have specific OSE and isolation rules. These calculators cover conventional hosts and VMs only; do not use VM totals as a container licensing answer.
Read the rule: Universal software terms · Windows Server 2025 licensing guidance · SQL Server 2025 licensing guidance
Check your understanding
Read the answer and explanation
No, reporting is an active workload. A secondary serving data to users is not passive under the failover terms. Assess its licensing separately.
Turn understanding into a checklist.
Collect the facts first. Then ask for a license inventory matched to your deployment.
Checklist and quiz choices stay in this page only. They are not saved or sent anywhere.
A small glossary for the buying conversation
- Core license vs. pack
- A two-core pack contains two core licenses. Always distinguish the number of packs from the number of licensed cores.
- SA
- Software Assurance: time-bound benefits attached to eligible licenses.
- HA / DR
- High availability keeps services available; disaster recovery restores them after a major outage. Their license conditions differ.
- Server farm
- A licensing-defined grouping used in mobility rules, not simply any servers your company owns.
- Multiplexing
- Pooling or routing connections through an intermediary. It does not automatically reduce required access licenses.
- Stacking
- Assigning more complete Standard host core-license sets to obtain more Windows Server OSE rights.
Check your understanding
Read the answer and explanation
16. Each pack contains two core licenses: 8 × 2 = 16.
Sources & verification
Last verified . Scope: Windows Server 2025 and SQL Server 2025, primarily commercial on-premises licensing. MCA Product Terms are the explicit cross-check used here; select your actual agreement before applying terms to a purchase.
- Windows Server 2025 licensing guidance
- SQL Server 2025 licensing guidance
- Windows Server Product Terms · MCA
- SQL Server Product Terms · MCA
- Universal software terms
- Software Assurance benefits
- Remote Desktop Services CALs
- SQL Server 2025 editions and limits
This is an educational guide, not a quote or confirmation of your entitlements. Microsoft’s applicable agreement and Product Terms control. Prices, complete legacy-version rules, and customer-specific compliance assessments are outside this guide.