SLA & Uptime Calculator
Translate availability targets into allowed downtime, or calculate achieved availability from an incident duration.
SLA to allowed downtime
Downtime to achieved availability
Availability and error budgets
An availability target defines the successful portion of a measurement window. Its complement is the error budget: a 99.9% SLO permits 0.1% unsuccessful time. Contractual SLAs may exclude scheduled maintenance or define availability from requests rather than minutes.
Measurement periods matter
Allowed downtime scales with the chosen window. This calculator uses 24-hour days, seven-day weeks, an average Gregorian month of 30.4375 days and a 365-day year.
Frequently asked questions
What does 99.9% uptime allow?
It permits 0.1% downtime: about 43 minutes 50 seconds in an average 30.4375-day month.
What is an error budget?
An error budget is the portion of a measurement period that may fail while an SLO is still met.
Does scheduled maintenance count as downtime?
That depends on the exact SLA contract. Use the calculator for arithmetic, then apply the exclusions defined by your agreement.