Uptime calculator
Convert an SLA uptime percentage into the downtime it actually allows per day, week, month and year, or work backwards from the downtime you observed to the percentage it produced. It all runs in your browser: nothing is sent anywhere and no account is needed.
What a percentage really costs you
A 99.9% target sounds close to perfect until you convert it: it still allows about 44 minutes of downtime every month and nearly nine hours a year. Reading the percentage as time is the fastest way to see whether a service level matches what your users will actually tolerate.
How the periods are counted
A day and a week are exact. A month is counted as 30.44 days and a year as 365.25 days, the long-run averages that make the yearly figure agree with every published SLA table. Always convert against the period your contract is written for, because the same percentage buys very different amounts of time.
An estimate is not a measurement
This tool converts a number you typed. It cannot tell you what your uptime actually was. That figure comes from checks running against your service around the clock, from more than one network, with every failure confirmed from a second location before it counts as downtime.
These figures are an estimate, not a measurement: they are arithmetic on a percentage you typed, while your real uptime is whatever independent checks recorded over the period. How uptime is actually calculated or start measuring yours from 300+ locations.
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