Utilisation-based downsizing is a heuristic, not a guarantee. Average CPU hides burst patterns; memory pressure, IOPS, network ceilings, licensing and architecture differences don't show in these two numbers at all. Candidates keep your current CPU architecture and workload class to stay bootable and comparable, and the need is computed as current × utilisation × (1 + headroom), rounded up. Savings are hourly on-demand list prices × 730 h — same caveats as the TCO comparator: no spot/reserved/committed rates, no regional uplifts, EUR never compared to USD. Benchmark before you resize.