Calculate allowed downtime for any SLA uptime percentage.
| Period | Allowed Downtime |
|---|
| Uptime | Name | Downtime/Year | Typical Use |
|---|---|---|---|
| 99% | Two Nines | 3.65 days | Internal tools |
| 99.9% | Three Nines | 8h 45m | Most SaaS, business apps |
| 99.95% | Three and a Half | 4h 22m | E-commerce, APIs |
| 99.99% | Four Nines | 52m 35s | Financial, healthcare |
| 99.999% | Five Nines | 5m 15s | Telecom, critical infra |
Downtime = Total time × (1 - uptime%). For example, 99.9% uptime over a year: 365.25 × 24 × 60 × (1 - 0.999) = 525.96 minutes = 8 hours 45 minutes.
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