Uptime / SLA Downtime Calculator

Formula

How this is calculated

Enter the availability percentage promised by your Service Level Agreement (SLA), such as 99.9%. The calculator first converts this to a downtime fraction with frac = 1 − availability / 100. For 99.9% that fraction is 0.001, meaning 0.1% of every period may be unavailable.

That fraction is multiplied by the length of each period in seconds to find the allowed downtime. The periods use fixed lengths: a day = 86,400 s, a week = 604,800 s, a month = 2,629,746 s (1/12 of an average Gregorian year), and a year = 31,556,952 s. So for 99.9% the yearly budget is 0.001 × 31,556,952 ≈ 31,557 s, which is about 8 h 45 m. Each result is then broken into days, hours, minutes and seconds for readability.

The input must be between 0 and 100. A value of 100% yields zero allowed downtime, while 0% means the service may be down the entire period. The month length is an average; calendar months of 28–31 days will differ slightly, and leap years add a day to the calendar year, so treat these figures as planning estimates rather than contractual guarantees.