How much downtime is 99.9%?
Pick an uptime target and see exactly how much downtime it allows per day, week, month, quarter and year — then share the result.
| Period | Allowed downtime |
|---|---|
| Per day | 1m 26s |
| Per week | 10m 5s |
| Per month | 43m 48s |
| Per quarter | 2h 11m 24s |
| Per year | 8h 45m 36s |
The nines, in plain numbers
| Uptime | Name | Per year | Per month | Typical for |
|---|---|---|---|---|
| 99% | Two nines | 3d 15h 36m | 7h 18m | Internal tools, batch jobs, hobby projects |
| 99.5% | Two and a half nines | 1d 19h 48m | 3h 39m | Small business sites, staging environments |
| 99.9% | Three nines | 8h 45m 36s | 43m 48s | Standard SaaS and e-commerce targets |
| 99.95% | Three and a half nines | 4h 22m 48s | 21m 54s | Business-critical SaaS, B2B platforms |
| 99.99% | Four nines | 52m 34s | 4m 23s | Payments, core infrastructure, APIs others depend on |
| 99.999% | Five nines | 5m 15s | 26.28s | Telecom, emergency and safety-critical systems |
What counts as downtime?
The percentage is only as honest as the definition behind it. Agree on these three before you sign anything.
Planned maintenance
Many SLAs exclude announced maintenance windows. Check how much notice is required and how long a window may last.
Partial outages
If checkout is broken but the homepage loads, is that downtime? Define it per feature, not just per server.
Third-party failures
A payment provider or DNS outage can take you down. Decide whether you count it against your own target.
Go deeper on SLAs
How to calculate uptime from incident logs
A step-by-step method to turn a list of incidents into an honest monthly uptime percentage.
Read →BusinessThe cost of one hour of downtime
A simple way to estimate what an hour offline really costs your business, beyond lost sales.
Read →BasicsSLA vs SLO vs SLI: what is the difference?
Three similar acronyms, three different jobs. A plain explanation with a worked example.
Read →Know your real uptime
Upzilla measures availability minute by minute and gives you the number your SLA is actually based on.