Uptime and SLA calculator
A 99.9% SLA sounds near perfect until you turn it into minutes: forty-three minutes of outage a month. Each extra nine divides the downtime budget by ten.
A month is taken as 30.44 days, the annual average, because real months differ. Most contracts exclude announced maintenance, so the downtime that counts against an SLA is usually lower than the observed one.
Frequently asked questions
How much downtime does each tier allow?
Per month: 99% allows 7 hours 18 minutes, 99.9% allows 43 minutes, 99.95% allows 21 minutes, 99.99% allows 4 minutes 23 seconds, and 99.999% allows 26 seconds.
What is an error budget?
The gap between promised and achieved uptime, expressed as time. How long you can still be down in the current period without breaching — useful when deciding whether to ship something risky this month.
Is planned maintenance deducted?
In most contracts yes, if it was announced within the agreed window. It is why a provider's reported uptime is almost always better than the one users perceive.