Question 1

How much downtime does 99.9% uptime allow per year?

Accepted Answer

99.9% uptime (three nines) allows approximately 8 hours 45 minutes of downtime per year, 43 minutes 49 seconds per month, and 10 minutes 4 seconds per week.

Question 2

How much downtime does 99.99% uptime allow?

Accepted Answer

99.99% uptime (four nines) allows approximately 52 minutes 35 seconds of downtime per year, 4 minutes 22 seconds per month, and about 1 minute per week.

Question 3

What is five nines (99.999%) uptime?

Accepted Answer

Five nines (99.999% uptime) allows only about 5 minutes 15 seconds of downtime per year — roughly 26 seconds per month. This is the gold standard for mission-critical systems and financial infrastructure.

Question 4

How is downtime cost calculated?

Accepted Answer

Downtime cost is estimated by dividing your monthly revenue by the number of hours in a month to get an hourly revenue figure. This is then multiplied by the hours of downtime your SLA allows. The actual loss depends on when downtime occurs and whether all revenue is truly at risk.

SLA	Per Year	Per Month
99%	3d 15h	7h 18m
99.5%	1d 19h	3h 39m
99.9%	8h 46m	44 minutes
99.95%	4h 23m	22 minutes
99.99%	53 minutes	4 minutes
99.999%	5 minutes	< 1 minute

Uptime & Downtime Calculator

Downtime Allowance

Common SLA Reference