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Availability Calculator

Calculate how much downtime should be permitted in your Service Level Agreement.

"In general, for any software service or system you can think of, 100% is not the right reliability target because no user can tell the difference between a system being 100% available and, let's say, 99.999% available." - Ben Treynor

Availability Table(Cheat Sheet)

AvailabilityDowntime per yearDowntime per quarterDowntime per monthDowntime per weekDowntime per dayDowntime per hour
90%36.52 days9.13 days3.04 days16.80 hours2.40 hours6.00 minutes
95%18.26 days4.57 days1.52 days8.40 hours1.20 hours3.00 minutes
99%3.65 days21.91 hours7.30 hours1.68 hours14.40 minutes36.00 seconds
99.5%1.83 days10.96 hours3.65 hours50.40 minutes7.20 minutes18.00 seconds
99.9%8.77 hours2.19 hours43.83 minutes10.08 minutes1.44 minutes3.60 seconds
99.95%4.38 hours1.10 hours21.91 minutes5.04 minutes43.20 seconds1.80 seconds
99.99%52.59 minutes13.15 minutes4.38 minutes1.01 minutes8.64 seconds0.36 seconds
99.999%5.26 minutes1.31 minutes26.30 seconds6.05 seconds0.86 seconds0.04 seconds
Calculations are based on the average Gregorian year: 365.2425 days


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