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upcertain

Calculator

Uptime and downtime calculator

Turn an uptime target such as 99.9% into the downtime it allows per day, week, month, quarter and year, or work out the uptime left after an outage.

Downtime allowed by an uptime target

A year is 365 days and a month 30 days.

Per day
1 m 26 s
Per week
10 m 5 s
Per 30-day month
43 m 12 s
Per 90-day quarter
2 h 9 m 36 s
Per 365-day year
8 h 45 m 36 s

Uptime after a given downtime

Uptime99.9306%

Common uptime targets

UptimeDayWeekMonthQuarterYear
99%14 m 24 s1 h 40 m 48 s7 h 12 m21 h 36 m3 d 15 h 36 m
99.5%7 m 12 s50 m 24 s3 h 36 m10 h 48 m1 d 19 h 48 m
99.9%1 m 26 s10 m 5 s43 m 12 s2 h 9 m 36 s8 h 45 m 36 s
99.95%43.2 s5 m 2 s21 m 36 s1 h 4 m 48 s4 h 22 m 48 s
99.99%8.64 s1 m4 m 19 s12 m 58 s52 m 34 s
99.999%0.86 s6.05 s25.92 s1 m 18 s5 m 15 s

Months are 30 days, quarters 90 days and years 365 days. For what these numbers mean in practice, and why measured uptime depends on the check interval, read what 99.9% uptime means and how often to check.

The formula

Allowed downtime = (100 - uptime %) / 100 x length of the period. At 99.9% over a 30-day month that is 0.001 x 2,592,000 seconds = 2,592 seconds, or 43 minutes 12 seconds. The other way round, uptime = 100 - downtime / period x 100: 30 minutes of downtime in a 30-day month is 99.93%.

Questions

How much downtime is 99.9% uptime?
1 minute 26 seconds a day, 43 minutes 12 seconds in a 30-day month and 8 hours 45 minutes 36 seconds in a 365-day year.
How much downtime is 99.99% uptime?
About 8.6 seconds a day, 4 minutes 19 seconds a month and 52 minutes 34 seconds a year.
Why does my monitor report different uptime?
Measured uptime depends on how often you check, what counts as down and whether maintenance is excluded. A monitor checking every 5 minutes misses most short outages and reports higher uptime than one checking every 30 seconds.
Does the calculator send my numbers anywhere?
No. It runs in your browser.