How few new servers replace the ones you have?

It depends almost entirely on memory, not on cores. Replacing 2017-era two-socket servers with a current two-socket machine typically lands between 4:1 and 10:1, because a modern host carries four to eight times the memory and two to four times the cores. This calculator does not quote you a ratio — it derives one from the ceilings of the specific machine you pick, which is the only way the number means anything.

Because vCPU can be overcommitted and memory should not be. A 4:1 vCPU-to-core ratio is routine in production, so core demand divides down by four; memory does not divide at all, since ballooning and swapping are exactly how consolidation projects turn into performance incidents. That asymmetry is why this tool sizes both independently and tells you which one is binding — most calculators only count cores and land on a host count that cannot hold the workload.

Almost always, and it is on by default. Without it, a single host failure leaves the survivors carrying the full load with no headroom, which is the same as having no failover at all. On a small cluster N+1 is a significant proportion of the cost, which is a real argument for fewer, larger hosts — and an argument against them, since each failure then takes more workload with it.

More than people expect, because old servers idle badly. The calculator compares your current estate’s draw against the provisioned power of the target machine at the load factor you set, using power-supply configurations taken from each model’s own manufacturer document, then prices the difference at your tariff and converts it with the UK government’s 2026 emissions factors. It will also tell you when consolidation increases draw — which is what happens when you consolidate onto accelerator platforms, where the point is capability rather than efficiency.

Often, but not automatically, and it is the detail that decides whether a refresh pays for itself. Per-core licensing (VMware, Windows Server Datacenter, SQL Server) responds to total cores, so consolidating onto fewer but much denser hosts can leave the core count — and the bill — unchanged or higher. Per-socket and per-host models behave differently again. Our licensing calculator works that side, and it is worth doing both before committing.

From each model’s own manufacturer technical document — the maximum cores its processor table supports, the memory ceiling it states, its rack height and the power supplies it takes. The same verified library behind our 108 data sheets. Your current estate is your figures, with indicative presets by generation for anything you do not have to hand.