Fork me on GitHub

Availability Calculator

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

"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