Uptime calculator (SLA)
Convert an availability percentage (SLA) to allowed downtime, and calculate what multiple components achieve together.
Allowed downtime
| Period | Maximum downtime |
|---|
Reverse: what is my percentage?
Multiple components together
A chain is only as strong as its weakest link: if one component fails, everything fails. A component you run redundantly (two in parallel) is much more reliable.
| Component | Availability (%) | Redundant |
|---|
Availability (uptime) is the portion of time that something works. 99.9% sounds like almost always, but still means about 8.8 hours of downtime per year. Each additional nine makes it ten times stricter: 99.99% is only about 53 minutes per year. Such an agreement is called an SLA.
We calculate with a year of 365.25 days. The example figures for the home server example are estimates; use your own measurements or agreements. Also check whether a provider counts scheduled maintenance as downtime. Want to see how your own site is doing? Check the status page. Everything happens in your browser.