Licensed by physical core with a minimum you cannot avoid, and then again by everyone who connects. Here is how the maths actually works.
Microsoft PartnerVerify on Microsoft Marketplace →Windows Server is not licensed per server or per installation. It is licensed by the physical cores in the machine, and then again by the people or devices that connect to it. Both halves are needed and the second half is the one that gets forgotten.
One per physical core. Minimum 8 per processor and 16 per server, whatever the machine actually has. Sold in 2-packs and 16-packs.
A single-socket 8-core server still needs 16 core licences.
Licensed by physical cores, Standard permits two operating system environments. Datacenter permits unlimited.
The crossover is usually three to five virtual machines on one host.
Every user or device connecting to the server needs one. User CAL covers one person on any device; Device CAL covers one device used by anyone.
Bought separately from the server licence. Always.
Additional CALs required for Remote Desktop Services, including for use of the graphical interface, on top of the Base CAL.
Two CALs per remote user, not one.
Server licensing is arithmetic, and the arithmetic has traps in it. These are the ones that turn up in real quotes, in both directions — companies buying far more than they need, and companies discovering a shortfall at the worst possible moment.
Windows Server is licensed by physical core, with a minimum of 8 core licences per physical processor and 16 core licences per server. A single-socket box with 8 cores still needs 16 core licences. Core licences are sold in 2-packs and 16-packs, so the usual starting point is one 16-pack per server.
You license the physical cores present, not the cores assigned to virtual machines. A dual-socket server with 12 cores per processor needs 24 core licences, not 16.
Licensed by physical cores, Standard permits two OSEs — physical or virtual. Datacenter permits an unlimited number. The crossover point is usually somewhere between three and five virtual machines on the same host: past that, stacking Standard licences costs more than buying Datacenter once.
Every user or device that accesses the server needs a Windows Server CAL — the Base CAL — and it is bought separately. This is the line most often missing from a quote, and the one most often found during an audit.
A User CAL covers one person on any number of devices. A Device CAL covers one device used by any number of people. Sales staff with a laptop and a phone each are cheaper on User CALs. A warehouse with three shifts sharing eight terminals is far cheaper on Device CALs.
If users connect to a remote desktop or run applications through a session host, they need an RDS CAL in addition to the Base CAL — including for use of the graphical interface. Two CALs per user, not one. Budgets that missed this are typically out by a meaningful amount.
Licensing rules on this page were checked against Microsoft’s own documentation in September 2026. Microsoft changes plan contents regularly — if you are reading this much later, ask us to confirm before you commit to a term.
Count the physical cores in the server. You need one core licence per physical core, subject to a minimum of 8 per processor and 16 per server. Core licences come in 2-packs and 16-packs. Then add a CAL for every user or device that connects, and an RDS CAL on top for anyone using remote desktop.
Yes. The server licence covers the server software. Every user or device that accesses it needs a Windows Server CAL, bought separately. Missing CALs is the commonest licensing shortfall found in an audit.
A User CAL permits one named user to connect from any device. A Device CAL permits one device to be used by any number of users. Which is cheaper depends on whether you have more people than devices or more devices than people.
Virtualisation rights. Licensed by physical cores, Standard permits two operating system environments; Datacenter permits unlimited. If you are running more than about four virtual machines on one host, Datacenter usually works out cheaper than stacking Standard licences.
If users connect to the server through Remote Desktop or run applications on a session host, yes — an RDS CAL in addition to the Base CAL, including for use of the graphical interface. They are not a substitute for the Base CAL.
Yes, and it is the sensible first step. Send the server make and model, the processor count and cores per processor, how many virtual machines you plan to run, and how many people and devices connect. We come back with the core packs and CAL count, and tell you if Datacenter is the cheaper answer.
Tenant setup, mailbox and file migration, user onboarding and activation are included at no extra charge on Microsoft licences bought from Proto Link. You pay for the licences, not for the project around them.
Send us your headcount and what your team actually needs. We will come back with the right plan mix and a price — usually the same working day.