Guide · Server Licenses
Correctly Licensing Windows Server and SQL Server
Microsoft licenses servers using the Server-plus-CAL model. The server license only covers the hardware. Each user and device accessing the server also needs an access license, known as a CAL.
The rule of thumb for quantity: You need as many access licenses as you have users or devices, whichever number is smaller. Those working via Remote Desktop also need RDS access licenses.
Windows Server 2016: Support ends on January 12, 2027. The four options in a cost comparison shows which option is the most affordable.
- Volume licenses with documented origin
- Invoice with stated VAT
- Consultation on license quantity before purchase
- Auditable Proof Chain
Standard or Datacenter?
Both editions are functionally largely identical. The difference lies almost exclusively in the virtualization rights. If you run at most two virtual machines, Standard is the more economical choice.
| Server 2025 Standard | Server 2025 Datacenter | |
|---|---|---|
| Virtual Instances | 2 per license | unlimited on licensed hardware |
| Included Cores | 16 | 16 |
| Storage Spaces Direct | not included | included |
| Software Defined Networking | not included | included |
| Access Licenses Required | yes, per user or device | yes, per user or device |
| Typical Use | File, print, and application servers | Virtualization hosts and data centers |
| Preis | auf Anfrage | auf Anfrage |
| Anfragen→ | Anfragen→ |
The Server plus CAL model in one sentence
The server license allows the software to be run on the hardware. It does not allow anyone to access it. Any access is additionally covered by an access license, in English Client Access License, or CAL for short.
This is where most licensing errors occur. A company buys the server, installs it, everything runs, and nobody thinks about the CALs. Technically, this is never noticed because Windows Server does not count accesses. In an audit, it is immediately apparent.
User CAL or Device CAL
Both variants usually cost about the same but cover different things.
- User CAL: tied to a person. This person can access from any number of devices, be it a desktop, laptop, or mobile phone.
- Device CAL: tied to a device. Any number of people can access through this device.
The decision rule is simple: count people, count devices, and license the smaller number. An office with 10 employees using 14 devices needs 10 User CALs. A shift operation with 20 people using 6 terminals needs 6 Device CALs.
You can mix both types on the same network. This is worthwhile if some of the workforce works remotely and another part shares fixed workstations.
RDS CALs are in addition, not instead
If you work on the server via Remote Desktop, i.e., operate a terminal server or publish applications, you need a second access license on top of that. The RDS CAL does not replace the normal CAL; it supplements it.
Therefore, a workstation with Remote Desktop costs two licenses: the normal access license and the RDS access license. Here too, both variants are available, user-based and device-based, and the same rule applies.
This is by far the most common licensing error in small and medium-sized businesses.
Core Licensing and the 16-Core Rule
Since version 2016, Windows Server has been licensed per processor core, not per processor. Two minimums apply:
- at least 8 cores per physical processor,
- at least 16 cores per server.
A server with an 8-core processor will therefore still be licensed with 16 cores. Our standard license covers exactly these 16 cores. If your machine has more, core packs are added, usually in increments of two.
Important for planning: The physically present cores of the machine count, not those assigned to a virtual machine.
Which CAL fits which server
Access licenses must never be older than the server they are accessing. A CAL for Server 2019 does not cover Server 2022.
The opposite, however, does work: a CAL for Server 2025 also covers older servers. So, if you plan to update in the foreseeable future, you are better off with newer access licenses, even if the server is still one generation behind.
In mixed environments, always base your decision on the newest server in the network.
SQL Server follows its own rules
The configurator above calculates Windows Server. SQL Server has its own licensing model with two options: either server plus CALs, which is worthwhile for a manageable number of users, or licensing by cores, which pays off for many or an unknown number of accesses, such as for a web application. The Enterprise Edition is exclusively licensed by cores.
For SQL, the calculation decides: As long as the number of users is small and known, server plus CALs is almost always cheaper.
Frequently Asked Questions about Server Licensing
Do I need CALs if only I access the server?
Yes. Even a single access is an access. You need at least one user or device CAL in addition to the server license.
What is the difference between Standard and Datacenter?
The essential difference lies in the virtualization rights. Standard allows for two virtual instances per license, Datacenter an unlimited number on the licensed hardware. Additionally, Datacenter includes Storage Spaces Direct and Software Defined Networking.
Does an RDS CAL replace the normal access license?
No. The RDS CAL is additional. A Remote Desktop workstation requires both a standard Windows Server CAL and an RDS CAL.
Can I mix user and device CALs?
Yes. This is expressly permitted and often the most cost-effective solution when one part of the workforce works remotely and another part shares fixed workstations.
What is the minimum number of cores I need to license?
At least 16 cores per server and at least 8 cores per physical processor. Therefore, even a server with only 8 physical cores will be licensed for 16.
May CALs be older than the server?
No. Access licenses must at least match the server's version. Newer CALs, however, cover older servers.
Are used server licenses and CALs legal?
Yes. In 2012, the European Court of Justice ruled in Case C-128/11 that perpetual software licenses may be resold within the EU. The prerequisites are a complete chain of proof and that the previous owner no longer uses their copy.
Which licenses do you really need?
Answer three questions and you will receive the exact combination of server license and access licenses, including quantity and total price.
The recommendation follows the rule: as many access licenses as users or devices, whichever is less. Access licenses must never be older than the server they access. Newer CALs, however, cover older servers.
Further reading: Server Guide
In-depth articles on licensing models, editions, and access licenses.
