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How much downtime does your SLA allow?
Turn an uptime percentage into the downtime it allows per day, week, month, quarter and year, or work out the uptime a given amount of downtime leaves.
Allowed downtime
- Per day
- 1m 26s
- Per week
- 10m 4s
- Per month
- 43m 49s
- Per quarter
- 2h 11m 29s
- Per year
- 8h 45m 57s
99.9% uptime allows 43m 49s of downtime per month and 8h 45m 57s per year.
99.794%
uptime per month. Within a 99.5% SLA. 99.9% allows 43m 49s per month.
An SLA is only as good as the outages you notice. Uptimecheck checks as often as every minute and reports uptime against your target.
Monitor your uptime//_01 The nines
Allowed downtime for common uptime targets
A month is 30.44 days and a year 365.25 days, the averages over four years. Downtime is rounded down to the second.
| Uptime | Per day | Per week | Per month | Per year |
|---|---|---|---|---|
| 90% one nine | 2h 24m | 16h 48m | 3d 1h 3m | 36d 12h 36m |
| 95% | 1h 12m | 8h 24m | 1d 12h 31m 30s | 18d 6h 18m |
| 99% two nines | 14m 24s | 1h 40m 48s | 7h 18m 18s | 3d 15h 39m 36s |
| 99.5% | 7m 12s | 50m 24s | 3h 39m 9s | 1d 19h 49m 48s |
| 99.9% three nines | 1m 26s | 10m 4s | 43m 49s | 8h 45m 57s |
| 99.95% | 43s | 5m 2s | 21m 54s | 4h 22m 58s |
| 99.99% four nines | 8s | 1m | 4m 22s | 52m 35s |
| 99.999% five nines | 864ms | 6s | 26s | 5m 15s |
//_02 How it’s measured
What an uptime SLA actually counts
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01
Measured over calendar time
Uptime is the share of a period, usually a calendar month, that a service was up. Nights and weekends count as much as office hours, so an outage at 3 a.m. uses up the same budget as one at noon.
-
02
Planned maintenance is often left out
Most SLAs exclude maintenance announced in advance, within limits, and causes outside the provider’s control. Unannounced work counts. What is excluded is in the contract’s definition of downtime.
-
03
What counts as down
Usually the service not answering, or answering with errors, as seen from outside. Some agreements also count slow responses, or only outages longer than a few minutes. Credits are typically a share of the monthly fee, and only when you claim them.
How Uptimecheck measures uptime
Your sites are checked from Stockholm as often as every minute, and a failed check is confirmed by a second one before it counts as an outage. Uptime is the monitored time without a confirmed outage. Monitors aren’t checked during a maintenance window, so planned work never counts as downtime, and time a monitor was paused is left out. Reports show uptime per monitor for any period against an SLA target from 99% to 99.99%.
Questions
How much downtime is 99.9% uptime?
43 minutes and 49 seconds in an average month, 8 hours 45 minutes and 57 seconds in a year, 10 minutes and 4 seconds in a week and 1 minute and 26 seconds in a day. In a 31-day month it is 44 minutes and 38 seconds, in a 30-day month 43 minutes and 12 seconds.
What is the difference between 99.9% and 99.99% uptime?
Each extra nine allows ten times less downtime. 99.9% allows 8 hours 45 minutes a year; 99.99% allows 52 minutes and 35 seconds, or 4 minutes and 22 seconds a month. At 99.99%, one slow deploy or a single outage that takes ten minutes to notice uses up more than two months of downtime.
Does planned maintenance count as downtime?
It depends on the agreement. Most SLAs leave out scheduled maintenance that was announced in advance, often with a cap on how long or how often it may happen, while unannounced work counts. Read the definition of downtime in the contract. In Uptimecheck, monitors aren’t checked during a maintenance window, so that time never counts as downtime.
How does Uptimecheck calculate uptime in its reports?
Uptime is the share of the monitored time without a confirmed outage. A failed check is confirmed by a second check before it counts. Time a monitor was paused, before it was created, or when our own checks weren’t running is left out instead of counted as up or down. Reports show uptime per monitor for any period against an SLA target from 99% to 99.99%.
Why is a month 30.44 days here?
An SLA usually covers calendar months, which have 28 to 31 days. This calculator uses the average month, a year of 365.25 days divided by 12, so the numbers add up over a year. Allowed downtime is rounded down to the second, so staying within it keeps you within the SLA.
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