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ft:publication_title :

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# Microsoft Per Core (with CAL) licensing rules

# Microsoft Per Core (with CAL) licensing rules {#ariaid-title1}

Release version: Brazil  
Updated September 10, 2026  
![](https://www.servicenow.com/docs/portal-asset/ico-clock) 3 minutes to read
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## Summary of Microsoft Per Core (with CAL) licensing rules

The Microsoft Per Core (with CAL) licensing model applies to various Microsoft Server products such as Windows Server, System Center, and Core Infrastructure Server Suite.
It determines licensing requirements based on the number of installations and operating system environments (OSE).
This model has distinct rules for on-premise and cloud installations, with cloud licensing following Bring Your Own License (BYOL) principles.
Show full answer Show less  
For on-premise installations, licensing can be done either by physical cores on hosts or by individual virtual machines (VMs), but not by clusters. The ServiceNow Software Asset Management (SAM) application supports both methods and can automate allocation to optimize licensing costs.

## Licensing by Physical Cores

* **Applicability:** Introduced by Microsoft in 2016, this method licenses physical servers based on the number of cores.
* **Licensing requirements:** Licenses equal the number of physical cores; calculated as CPU count multiplied by core count.
* **Minimum licenses:** 8 licenses per physical processor, or 16 per server.
* **Client Access Licenses (CALs):** Required for users or devices accessing the server.
* **Virtualization rights:** For Windows Server Standard, licensing all cores grants rights to run 2 VMs with license stacking available for additional 2 VMs per re-licensing. For Windows Server Datacenter, licensing all cores grants rights to run unlimited VMs.
* **License mobility:** Not supported for Windows Server; licenses can be reassigned every 90 days to different servers.
* **Cluster virtualization considerations:** When using cluster technologies like VMware vSphere or Microsoft Hyper-V, all physical hosts that a VM could potentially migrate to must be licensed accordingly, due to live migration capabilities.

## Licensing by Individual Virtual Machines

* **Applicability:** Introduced by Microsoft in 2022, this method licenses virtual machines directly based on their virtual cores.
* **Licensing requirements:** Licenses equal the number of virtual cores on the VM; calculated as CPU count × core count × CPU thread count.
* **Minimum licenses:** 8 licenses per virtual machine.
* **License type:** Requires Software Assurance or subscription licenses.
* **License mobility:** Supported within the same server farm without the 90-day reassignment restriction. The 90-day rule applies only when moving licenses to a different server farm or cloud provider.

## Practical Implications for ServiceNow Customers

* Customers managing Microsoft Server licenses can use ServiceNow SAM to automate license allocation and optimize costs based on Microsoft licensing rules.
* Understanding whether to license by physical cores or by virtual machines depends on your environment, virtualization technology, and whether you have Software Assurance or subscription licenses.
* For clustered environments with live migration, ensure all potential host servers are licensed to remain compliant.
* Be mindful of CAL requirements and virtualization rights to avoid under-licensing or excessive licensing costs.  
The Per Core (with CAL) metric licensing model is followed by various Microsoft Server products such as Windows Server, System Center, and Core Infrastructure Server Suite. The number of licenses depends on the number of installations and operating system environments (OSE).

The licensing rules for on-premise installations of these products and the cloud installations are separate. The cloud licensing rules follow Bring Your Own License (BYOL). For more information, see [Licensing rules for BYOL and BYOS](https://www.servicenow.com/docs/_icj6X1kkCd82SpqwTrsTA "View the bring your own license (BYOL) licensing rules for Microsoft and Oracle products in public cloud environments. In addition, view bring your own subscription (BYOS) licensing rules for Red Hat Enterprise Linux (RHEL) products in public cloud environments. Licensing rules can differ for virtual machines that reside on shared hosts or dedicated hosts across different cloud providers.").  
To license the on-premise installation of these products using the Per Core (with CAL) licensing model, consider the following two options.

* Licensing by physical cores, also known as licensing by physical hosts
* Licensing by individual virtual machines

{#microsoft-percore-withcal__ul_zdd_3ym_qbc}  
Note:  
You can either allocate to individual hosts or individual virtual machines, not to cluster.  
You can either allocate manually, or the Software Asset Management application can automatically select the most cost-effective licensing option based on optimization criteria. For more information about how to perform allocation, see [Allocation management](https://www.servicenow.com/community/sam-blog/allocation-management-on-servicenow-sam-pro/ba-p/2649232) and how the Software Asset Management application performs automated optimization, see [View realized and potential cost-based licensing optimizations for Microsoft](https://www.servicenow.com/docs/xlWhMsU2Lg8HFzuVpzYtyg "View the realized and potential cost-based licensing optimizations for your Microsoft software products. Gain an in-depth understanding of each licensing optimization so that you can maximize cost savings across your Microsoft deployments.").  
Note:  
Both options, whether licensing by physical cores or licensing by individual virtual machines, come with their own set of Microsoft rules that must be followed. For more information, see [Windows Server Standard, Datacenter, and Essentials](https://www.microsoft.com/licensing/terms/productoffering/WindowsServerStandardDatacenterEssentials/EAEAS).

## Licensing by physical cores {#microsoft-percore-withcal__section_m2r_czp_rbc}

The Software Asset Management application supports licensing by physical core rules, introduced by Microsoft in 2016.{#microsoft-percore-withcal__table_g5f_rzp_rbc__entry__3}

| Rule | Windows Server Standard | Windows Server Data Center |
|-|-|-|
| Required number of licenses | Equals the number of physical cores on the licensed server The physical cores on servers are equal to `CPU count * Core count`. ||
| Min licenses required | * 8 per physical processor * 16 licenses per server {#microsoft-percore-withcal__ul_cyq_yzp_rbc} ||
| CAL requirement | Device or user CALs are required for users or devices accessing the server ||
| Virtualization rights | Rights to use 2 virtual machines if all cores of the host are licensed with the option for license stacking Note: You must license the host again to get rights to use 2 additional virtual machines. | Rights to run unlimited virtual machines when all cores of the host are licensed |
| License mobility within Server Farms (Software assurance benefit) Note: License mobility isn't available for Windows Server. Licenses can be reassigned to servers as often as every 90 days. | Not supported ||
[Table 1. Licensing by physical core rules]

{#microsoft-percore-withcal__table_g5f_rzp_rbc}When deploying Microsoft products like Windows Server or System Center (using the core with CAL license model) on cluster virtualization technologies such as VMware vSphere, Microsoft Hyper-V, or Nutanix AHV, the number of licenses required for the physical host depends on the virtual machines that could potentially migrate to it within the cluster.

Technologies like VMware vMotion, which enables live migration of virtual machines across all hosts, and host affinity, which helps lock virtual machines to hosts within a cluster, manage the movement of virtual machines across
hosts. To understand more about cluster virtualization technology and its support on the Software Asset Management application, see [Understanding your cluster infrastructure](https://www.servicenow.com/docs/7SL~tOF2Zpck_wP~Q~ae~Q "Get a holistic and strategic analysis of all the entities in your clusters in one view on the Software Asset Management application.").

According to Microsoft licensing rules, if a virtual machine with a Microsoft product like Windows Server installed is hosted on one server but can potentially migrate to another, the destination server must be licensed as if the virtual machine is already running on it.

## Licensing by virtual machines {#microsoft-percore-withcal__section_tkt_nbq_rbc}

The Software Asset Management application supports licensing by individual virtual machines rules, introduced by Microsoft in 2022.
{#microsoft-percore-withcal__table_gpd_tbq_rbc__entry__2}

| Rule | Windows Server Standard and Windows Server Data Center ||
|-|-|-|
| Required number of licenses | Equals the number of virtual cores on the virtual machine The virtual cores on servers are equal to `CPU count * Core count * CPU thread count`. ||
| Min licenses required | 8 licenses per virtual machine ||
| Software assurance or subscription license Note: The option to license by virtual machine is only available with software assurance or a subscription license. | Required ||
| License mobility within Server farms (Software assurance benefit) Note: Licenses can be reassigned within the same server farm as often as needed. The 90-day rule applies only when moving to another server farm or cloud provider. | Supported ||
[Table 2. Licensing by individual virtual machines rules]

{#microsoft-percore-withcal__table_gpd_tbq_rbc}