Windows Server licensing — the plain-English guide

Windows Server is licensed in two parts. First you license the server itself — by physical cores, in 16-core minimum packs. Then you license every user or device that connects to it with a Client Access License (CAL).

Without both pieces, you're out of compliance even if everything technically works. Microsoft's licensing audits do happen.

Count physical cores across all CPU sockets. Minimum 8 cores per socket, minimum 16 cores per server. Round up. Then pick the edition.

Pick User CALs (per named user, any device) or Device CALs (per shared device, any user). Pick whichever model produces the lower count.

Rule of thumb: knowledge workers with multiple devices → User CALs. Shift workers sharing a workstation → Device CALs.

Remote Desktop Services (formerly Terminal Services) requires an additional RDS CAL on top of the standard CAL for every connecting user or device.

You cannot share standard CALs and RDS CALs across the User and Device models — pick one model per CAL type.

Small business with 1 Hyper-V host (16 cores, 2 CPUs), running 4 VMs. 20 employees, each with a laptop. 5 of them connect via Remote Desktop.