Infrastructure
Uptime Calculator
Calculate allowed downtime from an uptime target, or the uptime implied by observed outages. Includes reference values from 99% to 99.99%.
Uptime
99.9000%
Allowed / implied downtime
43 minutes, 11 seconds
Reference values
| Target | 30-day month | 365-day year |
|---|---|---|
| 99% | 7 hours, 12 minutes | 3 days, 15 hours, 36 minutes |
| 99.5% | 3 hours, 36 minutes | 1 day, 19 hours, 48 minutes |
| 99.9% | 43 minutes, 11 seconds | 8 hours, 45 minutes, 35 seconds |
| 99.95% | 21 minutes, 35 seconds | 4 hours, 22 minutes, 47 seconds |
| 99.99% | 4 minutes, 19 seconds | 52 minutes, 33 seconds |
How to use it
- Enter an uptime percentage, or enter downtime to derive uptime.
- Choose a 30-day month or 365-day year as the reporting window.
- Compare the result with common SLA reference values.
Example
99.9% uptime allows 43.2 minutes of downtime in a 30-day month and 8.77 hours in a 365-day year. 99.99% allows 4.32 minutes per 30-day month.
Privacy
All calculations run locally. No availability data is collected.
FAQ
Which month length does this use?
The default planning month is 30 days (720 hours). A year is 365 days unless you switch to 365.25 for leap-year averaging. These are standard operations conventions, not billing-cycle calendars.
Does 99.9% include planned maintenance?
Only if your contract says so. Some SLAs exclude announced windows. The calculator is mathematical; contract language still decides what counts.
Why do vendors advertise 99.9% and still have outages?
An SLA is a budget for downtime, not a promise of zero incidents. Use this tool to translate the budget into minutes you can actually operate against.
Next step
Need this wired into a real system?
Estimators and converters help you think. Delivery still needs contracts, environments, and an owner.