Convert an uptime percentage into the downtime it permits across each period.
Availability is easier to reason about as an allowance of minutes. Three nines sounds close to perfect but permits nearly nine hours of outage a year, which is why SLAs are negotiated in nines rather than percentages. An SLA number only becomes actionable once converted into the outage budget it grants, and into the mean time between failures your website must actually achieve.
Uptime Percentage
Downtime = period × (1 − availability ÷ 100)
Downtime = period × (1 − availability ÷ 100) Availability is easier to reason about as an allowance of minutes. Three nines sounds close to perfect but permits nearly nine hours of outage a year, which is why SLAs are negotiated in nines rather than percentages.
An SLA number only becomes actionable once converted into the outage budget it grants, and into the mean time between failures your website must actually achieve.
This calculator takes 3 inputs: Target or measured availability, Measurement period, Number of outages in the period. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.