Uptime & SLA Downtime Calculator
Enter an availability percentage to see how much downtime it allows per day, week, month and year.
How it works
Allowed downtime = (100% - availability) x period. The figures here assume a 7-day week, a 30-day month and a 365-day year. Each extra "nine" cuts the budget by ten: 99.9% ("three nines") allows about 8.8 hours a year, while 99.99% allows under an hour and 99.999% only about five minutes.
Remember an SLA is measured over a defined window and usually excludes planned maintenance, so read your provider's definition closely.
Frequently asked questions
How much downtime is 99.9% uptime?
About 43 minutes per 30-day month and 8 hours 46 minutes per year.
What does five nines mean?
99.999% availability, about 5 minutes 15 seconds of downtime per year.
Is 99.9% good enough?
It depends on the service. For internal tools it is usually fine; payment systems often target 99.99% or better.