Uptime / SLA Calculator

Turn an uptime percentage into the downtime it actually permits.

What you provide

Result

99.9% allows 43.2 min of downtime a month

At 99.9% you may be down 8.76 h in a year and still meet the target. Two things decide whether that number means anything: the window it is measured over — a monthly target resets the budget twelve times a year, an annual one does not — and what counts as downtime, since most agreements exclude scheduled maintenance, which is where the difference between a stated and an experienced availability usually lives.

Diagnostic telemetry
Per day
1.4 min
Per week
10.1 min
Per month (30 days)
43.2 min
Per quarter
2.19 h
Per year
8.76 h
Commonly called
three nines

What this cannot tell you

  • Calculated in your browser. Nothing you enter is uploaded or logged.
  • Uses a 30-day month and a 365-day year, which is the convention almost every agreement uses. A calendar-month agreement gives a slightly different budget in February and in a 31-day month.
  • Says nothing about what a specific agreement counts as downtime. Scheduled maintenance is excluded from most, which is where the gap between a stated and an experienced availability usually lives.
  • Service credits are not compensation for the loss. They are typically a small percentage of the monthly fee, and they have to be claimed.

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Uptime / SLA Calculator on RunTheTests — free browser-based sysadmin tools, no sign-up.