SLA Comparison Table

What each availability target actually allows, from 99% to five nines.

What you provide

Target to highlight

Result

99.9% allows 43.2 min of downtime a month

Each extra nine costs roughly ten times what the last one did, and buys back an order of magnitude less time. The step from 99.9% to 99.99% is the one where architecture changes: it leaves about four minutes a month, which is less than a person can notice a problem, log in and fix it, so recovery has to be automatic. Read the measurement window too. A monthly target hands back a fresh budget twelve times a year, and most agreements exclude scheduled maintenance, which is where a stated availability and an experienced one part company.

Downtime allowed

Check	Per day	Per month	Per year
99%	14.4 mininfo	7.20 hinfo	3.65 daysinfo
99.5%	7.2 mininfo	3.60 hinfo	1.82 daysinfo
99.9%	1.4 mininfo	43.2 mininfo	8.76 hinfo
99.95%	43.2 sinfo	21.6 mininfo	4.38 hinfo
99.99%	8.6 sinfo	4.3 mininfo	52.6 mininfo
99.999%	864 msinfo	25.9 sinfo	5.3 mininfo

Diagnostic telemetry

99%3.65 days a year: 7.20 h / month
99.5%1.82 days a year: 3.60 h / month
99.9%8.76 h a year: 43.2 min / month
99.95%4.38 h a year: 21.6 min / month
99.99%52.6 min a year: 4.3 min / month
99.999%5.3 min a year: 25.9 s / month

What this cannot tell you

A reference table computed from percentages. It does not measure any service and knows nothing about your actual availability.
Every agreement defines downtime differently. Scheduled maintenance, partial degradation and the measurement window all change what a percentage means in practice, and none of that is in the arithmetic.

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SLA Comparison Table on RunTheTests — free browser-based sysadmin tools, no sign-up.