Windows Server 2025 Standard and Datacenter are licensed per processor core. Every physical core in the server must be licensed, with a minimum of 8 core licences per processor and 16 per server. On top of that, every user or device that accesses the server needs a Client Access Licence (CAL). A small office with one modest server typically buys one 16-core Standard licence plus CALs for its staff.
How many core licences does a server need?
Count the physical cores, then apply the two minimums. Core licences are sold in 2-packs and 16-packs.
| Server | Physical cores | Core licences needed | How to buy |
|---|---|---|---|
| 1 processor, 8 cores | 8 | 16 (server minimum) | One 16-pack |
| 1 processor, 16 cores | 16 | 16 | One 16-pack |
| 2 processors, 12 cores each | 24 | 24 | One 16-pack plus four 2-packs |
| 2 processors, 16 cores each | 32 | 32 | Two 16-packs |
Source: Microsoft Windows Server 2025 licensing guidance. Compiled 12 November 2026.
CALC: a 2 x 12-core server has 24 cores. 24 - 16 = 8 extra cores, and 8 / 2 = four 2-packs.
Standard or Datacenter?
| Edition | Virtual machines allowed when all cores are licensed | Suits |
|---|---|---|
| Essentials | One server licence, sold with OEM hardware only, with user and device limits | Very small offices with a single small server |
| Standard | Two | Most SMEs |
| Datacenter | Unlimited | Hosts running many virtual machines |
Standard can be stacked. License all the cores a second time and you may run two more virtual machines.
CALC: four virtual machines on a 16-core host with Standard means licensing the 16 cores twice, so 32 core licences. Datacenter only becomes cheaper when a host runs many virtual machines; published licensing analyses put the crossover at roughly a dozen on a 16-core host. Below that, stacked Standard costs less.
What are CALs and who needs one?
A CAL is the right for a person or a device to use the server. You choose one type:
- User CAL. One per person, whatever devices they use. Usually right for offices where staff have a laptop and a phone.
- Device CAL. One per device, whoever uses it. Right for shared terminals on shift work.
CALs must be the same version as the server or later. Windows Server 2022 CALs do not license access to a 2025 server. Remote Desktop Services needs a separate RDS CAL in addition to the standard CAL.
The server licence is the smaller surprise. The CALs, and forgetting the RDS CALs, are where small-office budgets usually go wrong.
What does a small office pay?
Windows Server 2025 licences are quoted on request. The listed Windows Server 2022 OEM prices below give a working guide to the scale.
CALC, 20 users, one 16-core server: one Standard 16-core licence at S$1,275 plus four 5-user CAL packs at S$320. S$1,275 + S$1,280 = S$2,555.
CALC, same office on a 24-core server: S$1,275 + (4 x S$195 for 2-core add-on licences) = S$2,055, plus S$1,280 in CALs = S$3,335.
The difference between those two is S$780, caused only by choosing a processor with more cores. Size the processor to the workload and the licence bill follows.
What is a ROK licence?
ROK stands for Reseller Option Kit. It is an OEM licence sold by the server maker and locked to that maker's hardware. It is usually cheaper than volume licensing but cannot be moved to another brand of server. If you want the right to move a licence to new hardware later, ask about volume licensing instead.
Do you need Windows Server at all?
If the server will only share files, a NAS avoids both core licences and CALs. See server vs NAS for a small office. If you are licensing because an old server is going out of support, see Windows Server 2016 end of support. For choosing hardware, see ProLiant vs PowerEdge vs ThinkSystem.
Buying in Singapore
Prices below were listed on 12 Nov 2026; prices change; ask for a current quotation.
- Dell Microsoft Windows Server 2022 Essentials ROK (10 Core), S$525.
- Dell Microsoft Windows Server 2022 Standard ROK (16 Core), S$1,275.
- Dell Windows Server 2022 Standard additional licence (2 Core), S$195.
- Dell Microsoft Windows Server 2022/2019 CAL (5 User), S$320.
- HPE Microsoft Windows Server 2022 Standard ROK 16 Core, S$1,305.
- Lenovo Microsoft Windows Server 2022 Standard ROK (16 Core), S$1,345.
- Price on request: Windows Server 2025 Standard and Datacenter licences, Windows Server 2025 CALs and RDS CALs.
To start, use Request for Quotation on the product page, call (65) 6978 3502, email Sales@sourceit.com.sg or use our contact page.
Frequently asked questions
What is the minimum Windows Server 2025 licence? 16 core licences per physical server, even if the processor has fewer cores.
Do I need CALs if I already bought core licences? Yes. Core licences cover the server software. CALs cover the people or devices using it.
How many virtual machines does Standard allow? Two per fully licensed server. License the cores again for two more.
Can I reuse my old CALs? Only if they are the same version as the new server or later.
SourceIT Approved
Researched and verified by the SourceIT team for Singapore buyers.
