FinOps Right-Sizing Without Vibes: The 5-Number Recipe That Cuts $200k of Idle EC2

The average mid-size production EC2 fleet runs at 12 to 23 percent utilization. The remaining 77 to 88 percent is idle compute that ran continuously, billed continuously, and produced nothing. On a 200-instance fleet of m5.xlarge equivalents, that idle slice is worth $150,000 to $250,000 a year. The numbers come from AWS Trusted Advisor and the Flexera 2025 State of the Cloud report and they have not moved much in five years. Right-sizing should fix this. Most teams treat it as judgement-driven: