99.99% uptime: how much downtime?
An uptime of 99.99% (four nines) allows 4m 23s of downtime a month and 52m 34s a year.
| Period | Allowed downtime |
|---|---|
| Per day | 8.64 s |
| Per week | 1m |
| Per month | 4m 23s |
| Per quarter | 13m 8s |
| Per year | 52m 34s |
What 99.99% means in practice
About four and a half minutes a month. One manual response to an alert can use all of it, so detection and failover have to be automatic.
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.