Using this table in SLA negotiations
SLA tiers should be set conservatively relative to your internal SLO. If your engineering team targets 99.9% internally, committing to 99.9% externally gives you no buffer — any SLO breach immediately triggers an SLA violation.
A common practice is to set the external SLA 1–2 tiers below the internal SLO. If your SLO is 99.9%, your SLA commits to 99.5% — giving you over 35 additional hours per year before any contractual consequences.
Planned maintenance windows
Most SLAs explicitly exclude planned maintenance windows from availability calculations. If your service requires regular maintenance, ensure your SLA clearly defines what constitutes planned maintenance and how far in advance customers must be notified.
Interactive calculation
For a specific uptime percentage not shown in this table, use the Availability Calculator to compute exact downtime values for any SLA tier.