Define the reporting period and coverage
Covered hours, days, exclusions, planned maintenance, regional scope, and partial-impact rules determine the contractual calculation.
Handle overlapping events once
Overlapping outages should be merged so the same minute is not counted multiple times. Operational analysis should use the maximum concurrent impact percentage.
Separate SLA from SLO
The external agreement determines contractual status. An internal SLO and error budget can be more demanding and provide an earlier operating signal.
Estimate impact transparently
Affected users, productivity loss, labor cost, service value, and fixed incident overhead can create an estimate, but assumptions should remain visible and challengeable.
Apply the method
The related Greywake application exposes the inputs, assumptions, and output structure described in this article.