Usage rating transforms raw consumption data (API calls, gigabytes, transactions) into billable amounts by applying the correct pricing rules, tiered rates, and contract-specific terms. It is the core calculation engine of any metered billing system.

Example: A customer has consumed 750,000 API calls in a month. The usage rating engine applies the pricing rule: $0.01 per call for the first 100,000, $0.008 for the next 400,000, and $0.006 for anything above 500,000. The rated amount is $1,000 + $3,200 + $1,500 = $5,700.