Uptime Calculator — SLA Downtime Allowance
Enter your uptime target (e.g., 99.9 %) and instantly see how much downtime that allows per year, month, week, and day — plus where it sits on the "nines" reliability scale used in SLAs and cloud services.
%
Four nines (99.99 %)
Come funziona questo calcolatore?
Downtime allowance = (1 − uptime%) × period in seconds. For 99.9 % (three nines) that is ~8.77 h/year or 43.8 min/month. Five nines (99.999 %) cuts it to ~5.26 min/year. Each extra nine reduces allowed downtime tenfold.
Formula
How this is calculated
Uptime is the fraction of time a system or service is operational, typically expressed as a percentage of a calendar period. An uptime SLA of 99.9 % per year means the service is allowed to be down for at most 0.1 % of 365.25 × 24 × 3 600 = 31 557 600 seconds, which works out to ~8.77 hours per year or ~43.8 minutes per month.
The "nines" shorthand counts the consecutive 9s in the availability figure: 99 % is "two nines," 99.9 % is "three nines," and so on. Each extra nine reduces the allowed downtime by a factor of ten. This calculator uses the Julian year (365.25 days) for annual figures and divides uniformly for months (year÷12) and weeks.
Note that uptime SLAs measure scheduled availability and may exclude planned maintenance windows. Real services also face bursty failures, so a system can meet an annual SLA yet still cause significant disruption during a single outage event.
Domande frequenti
Three nines (99.9 %) allows about 8.77 hours of downtime per year, 43.8 minutes per month, 10.1 minutes per week, and 1.44 minutes per day.
Five nines means 99.999 % uptime — only about 5.26 minutes of downtime per year, or roughly 26 seconds per month. It is the gold standard for carrier-grade telecom and critical infrastructure.
Yes — a monthly SLA and an annual SLA for the same percentage translate to very different absolute downtime allowances. A 99.9 % monthly SLA allows 43.8 minutes per month but resets each month, while an annual SLA averages that over 12 months without a monthly reset.
TG we-Calculate Editorial Team. (2026). Uptime Calculator — SLA Downtime Allowance [Online calculator]. TG we-Calculate. https://we-calculate.com/it/calculator/uptime-calculator
TG we-Calculate Editorial Team. "Uptime Calculator — SLA Downtime Allowance." TG we-Calculate. 2026. https://we-calculate.com/it/calculator/uptime-calculator.
TG we-Calculate Editorial Team, "Uptime Calculator — SLA Downtime Allowance," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/it/calculator/uptime-calculator
@misc{wecalculate_uptime_calculator, title = {Uptime Calculator — SLA Downtime Allowance}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/it/calculator/uptime-calculator}}, year = {2026}, note = {TG we-Calculate} }
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