A service level agreement, or SLA, defines measurable service commitments between a provider and customer, together with the calculation rules, exclusions, reporting and consequences. A useful SLA turns a general promise such as “fast support” into a metric that both parties can reproduce from the same data.
What should an SLA define?
- Service, population and measurement period
- Metric formula, data source and time zone
- Target, threshold and allowed exclusions
- Incident severity and start or stop events
- Reporting, review and dispute procedure
- Service credits, remediation or escalation
How is SLA attainment calculated?
A common percentage formula is SLA attainment = compliant cases ÷ eligible cases × 100.
Illustrative SLA attainment calculation
| Step | Arithmetic | Result |
|---|---|---|
| Total cases | Cases recorded in the month | 1,020 |
| Approved exclusions | 1,020 − 20 | 1,000 eligible cases |
| Compliant cases | Cases completed within target | 970 |
| SLA attainment | 970 ÷ 1,000 × 100 | 97% |
The figures are illustrative. The result is meaningful only if the contract defines eligibility, exclusions and the event that starts and stops the clock.
SLA vs. key performance indicator
An SLA is a contractual service commitment. A KPI is a management measure and may not create a contractual remedy. The same metric can serve both purposes, but its contractual status and calculation rules should be explicit.
