Uptime and SLA calculator
Convert an SLA uptime percentage into the downtime it actually allows per day, week, month and year, or work backwards from the downtime you observed to the percentage it produced. It all runs in your browser: nothing is sent anywhere and no account is needed.
What a percentage really costs you
A 99.9% target sounds close to perfect until you convert it: it still allows about 44 minutes of downtime every month and nearly nine hours a year. Reading the percentage as time is the fastest way to see whether a service level matches what your users will actually tolerate.
Find out moreHow the periods are counted
A day and a week are exact. A month is counted as 30.44 days and a year as 365.25 days, the long-run averages that make the yearly figure agree with every published SLA table. Always convert against the period your contract is written for, because the same percentage buys very different amounts of time.
Find out moreAn estimate is not a measurement
This tool converts a number you typed. It cannot tell you what your uptime actually was. That figure comes from checks running against your service around the clock, from more than one network, with every failure confirmed from a second location before it counts as downtime.
Find out moreWhat 99.9%, 99.95% and 99.99% uptime allow
| Uptime target | Downtime per month | Downtime per year |
|---|---|---|
| 99.9% | 43m 50s | 8h 46m |
| 99.95% | 21m 55s | 4h 23m |
| 99.99% | 4m 23s | 52m 36s |
| 99.999% | 26s | 5m 15s |
Based on a 30.44-day average month and a 365.25-day average year, the same long-run averages the calculator above uses.
A percentage in a contract only holds up as an SLA when it is backed by monitoring that runs independently of your own infrastructure - see how distributed availability monitoring confirms it.
These figures are an estimate, not a measurement: they are arithmetic on a percentage you typed, while your real uptime is whatever independent checks recorded over the period. How uptime is actually calculated or start measuring yours from 300+ locations.
Key takeaways
- This calculator converts an uptime percentage into the downtime it allows per day, week, month and year, and converts a downtime figure back into a percentage.
- It is arithmetic in your browser: it runs no check, contacts no server and needs nothing about your site. A month is an average 30.44 days and a year 365.25 days.
- On that basis 99.9 percent uptime allows about 43 minutes 50 seconds of downtime a month, and 99.99 percent allows about 4 minutes 23 seconds.
- It is free, needs no login and no credit card.
- For continuous checks, see the distributed availability monitoring page: measured uptime comes from a monitor's own recorded history, not from a target figure.
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