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SLA & Uptime Calculator

How much downtime does 99.9% actually allow? Convert an SLA percentage into a concrete downtime budget — per day, week, month and year.

Common SLA targets

%

Allowed downtime

Per day
1m 26s
Per week
10m 4s
Per month
43m 49s
Per year
8h 45m 57s

Reverse: downtime budget → required uptime

min
of downtime per month requires

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The "nines" at a glance

SLA Nickname Downtime / day Downtime / month Downtime / year
99% Two nines 14m 24s 7h 18m 18s 3d 15h 39m
99.5% — 7m 12s 3h 39m 9s 1d 19h 49m
99.9% Three nines 1m 26s 43m 49s 8h 45m 57s
99.95% Three and a half nines 43s 21m 54s 4h 22m 58s
99.99% Four nines 8s 4m 22s 52m 35s
99.999% Five nines < 1s 26s 5m 15s

How the calculation works

An SLA (Service Level Agreement) expresses availability as a percentage of total time. The allowed downtime is simply the remaining fraction: at 99.9% uptime, 0.1% of the period may be down. Over a 30.44-day average month that is about 43.8 minutes; over a year, about 8 hours 46 minutes.

This calculator uses the average Gregorian month (30.44 days) and year (365.25 days), which is what most cloud providers and status pages use. Some contracts measure per calendar month instead — a 31-day month gives you slightly more budget than a 28-day February.

Beware of the measurement window: 99.9% per year allows a single 8-hour outage, but 99.9% per month caps any single month at ~44 minutes. The shorter the window, the stricter the SLA in practice.

Know when you're eating into your SLA budget

ContinuumNexus monitors your APIs from multiple regions and alerts you the moment they go down — before your downtime budget does.

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Frequently asked questions

How much downtime is 99.9% uptime per month?
99.9% uptime allows roughly 43 minutes 50 seconds of downtime per average month (30.44 days), or about 8 hours 46 minutes per year.
What does "five nines" mean?
"Five nines" is 99.999% availability — about 26 seconds of downtime per month or 5 minutes 15 seconds per year. It is extremely hard to achieve and usually requires redundant infrastructure across regions.
Is the calculation per calendar month or average month?
This tool uses the average month of 30.44 days (365.25 / 12), the convention used by most cloud SLAs. A contract measured per calendar month varies slightly: a 31-day month allows ~44.6 minutes at 99.9%.
Does scheduled maintenance count as downtime?
It depends on the contract. Many SLAs exclude announced maintenance windows from the availability calculation. Read the definition of "downtime" in your provider's SLA carefully — it is often narrower than users expect.
How do I actually measure my uptime?
You need an external monitor that checks your service at a regular interval from outside your own infrastructure, records failures, and computes availability over time — that is exactly what an uptime monitoring service like ContinuumNexus does.