It depends on the server hardware configuration, virtual desktop configuration, and desktop application.
The number of virtual desktops you can deploy on a server increases in the following situations:
The server has high CPU performance and memory size.
The CPU and memory resources assigned to each virtual desktop are low.
The desktop applications are not resource intensive. For example, an Office application is less complicated than AutoCAD and has lower hardware resource usage than AutoCAD.
When you plan VM deployment, reserve an amount of resources to ensure server stability. A production environment typically deploys HA and dynamic resource scheduling (DRS) features to make sure that the desktops are available and operate reliably. When CPU or memory resources on a server exhausted, DRS would move some VMs on that server to other servers.
As a best practice, make sure the desktop VMs deployed on a physical server use only two-thirds of server resources.
For example, a server has two CPUs, six CPU cores, and 128 GB memory. If you assign 1 vCPU and 2 GB memory to each desktop, you can theoretically run 50 to 60 desktops on the server. To ensure server stability, deploy a maximum of 40 desktops on the server.