How much downtime an availability target actually allows. Months are 30 days and years are 365, which is close enough for arguing about SLAs.

Tool

Allowed downtime:

1m 26s per day
10m 5s per week
43m 12s per month
8h 45m 36s per year
min

That's 99.9537% uptime for the month.

Cheat sheet

Target Per month Per year
99% 7h 12m 3d 15h 36m
99.9% 43m 12s 8h 45m 36s
99.95% 21m 36s 4h 22m 48s
99.99% 4m 19s 52m 34s
99.999% 26s 5m 15s