99.95% uptime: how much downtime?
An uptime of 99.95% (three and a half nines) allows 21m 54s of downtime a month and 4h 22m 48s a year.
| Period | Allowed downtime |
|---|---|
| Per day | 43.2 s |
| Per week | 5m 2s |
| Per month | 21m 54s |
| Per quarter | 1h 5m 42s |
| Per year | 4h 22m 48s |
What 99.95% means in practice
Around 22 minutes a month. It generally needs redundancy across more than one zone, and a deploy that goes wrong has to be reverted quickly.
A year is counted as 365 days and a month as a twelfth of that. Need another percentage, or the uptime from minutes of downtime? Use the uptime calculator.