Uptime (Availability)
Uptime (Availability): The percentage of time the service is operational.
Formula
Uptime = (Total time - Downtime) / Total time × 100Benchmarks
- 99.0%: ~7.3 hours downtime (unacceptable for most SaaS)
- 99.9%: ~43 minutes downtime (three nines)
- 99.95%: ~22 minutes downtime (typical SLA)
- 99.99%: ~4.3 minutes downtime (four nines, high reliability)
What It Tells You
Basic platform reliability.
Common Mistakes
- Excluding "scheduled maintenance" (customers don't care why it's down)
- Measuring only core service, not dependencies
- Not weighting by traffic/usage
Related Metrics
Connected in the GASP relationship graph.
Upstream: what drives this
- MTTR drives Uptime (Engineering)