SLA Uptime Calculator
How much downtime does your SLA allow?
Allowed downtime equals the length of the period × (1 − uptime %). So 99.9% uptime permits about 8h 45m per year; each extra “nine” cuts that roughly tenfold. Enter your target uptime below to see the budget per day, week, month, and year.
Downtime / day
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Downtime / week
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Downtime / month
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30.44-day average
Downtime / year
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Common uptime tiers
| 99% (two nines) | 3d 15h / year |
| 99.9% (three nines) | 8h 45m / year |
| 99.95% | 4h 22m / year |
| 99.99% (four nines) | 52m 35s / year |
| 99.999% (five nines) | 5m 15s / year |
Frequently asked questions
How much downtime does 99.9% uptime allow?
About 8 hours 45 minutes per year — roughly 43 minutes per month and 10 minutes per week.
What's the difference between 99.9% and 99.99%?
99.9% permits ~8h 45m of downtime a year; 99.99% permits only ~52 minutes. Each extra nine cuts allowed downtime by about 10×.
How is allowed SLA downtime calculated?
Period length × (1 − uptime/100). For a year that's 365 days × (1 − uptime/100).