The downtime table
Uptime is the share of time a service is working. The remaining time is the downtime the provider can have before it misses its target. Every 'nine' you add divides the allowance by ten.
| Uptime | Downtime per day | per week | per 30-day month | per year |
|---|---|---|---|---|
| 99% | 14 min 24 s | 1 h 41 min | 7 h 12 min | 3 days 16 h |
| 99.5% | 7 min 12 s | 50 min 24 s | 3 h 36 min | 1 day 20 h |
| 99.9% | 1 min 26 s | 10 min 5 s | 43 min 12 s | 8 h 46 min |
| 99.95% | 43 s | 5 min 2 s | 21 min 36 s | 4 h 23 min |
| 99.99% | 8.6 s | 1 min | 4 min 19 s | 52 min 34 s |
| 99.999% | 0.86 s | 6 s | 26 s | 5 min 15 s |
Try your own number
Uptime calculator
Type an uptime percentage to see how much downtime it allows.
- Per day
- 8.6 s
- Per week
- 1 min
- Per 30-day month
- 4 min 19 s
- Per year
- 52 min 34 s
Maximum downtime allowed, using a 365-day year and a 30-day month.
How uptime is measured
A monitoring service requests your page or checks your server at regular intervals, from one or more places, and records whether it answered correctly. The figure depends on choices that are easy to overlook:
- How often it checks. A check every minute notices a short outage that a check every ten minutes misses.
- What counts as down. A page that loads but shows an error is down to visitors even if the server answers.
- The measurement window. Uptime is usually reported per month. A bad hour weighs more in a month than in a year.
- Planned maintenance. Many SLAs exclude announced maintenance. Check whether yours does.
What an uptime SLA does and does not promise
A service level agreement (SLA) states the uptime a provider aims for. It is not a guarantee that nothing will go wrong, and no provider can promise that. What matters is what happens when the target is missed. When you read one, look for:
- the measurement window and how downtime is calculated;
- exclusions, such as scheduled maintenance, customer-caused problems and events outside the provider's control;
- the remedy: usually service credits rather than money back, and often only if you claim within a set time;
- whether the figure applies to every plan or only to some.
The engineers who run Google's services make a related point in the SRE book chapter on {ext(_SRE, "embracing risk")}: very high availability costs more with each extra nine, so the right target depends on what the service is for.
Judge a host by its record
The best evidence is history. A public status page that shows each monitor over time, including the bad days, tells you more than a headline percentage. Cloud Cabin's is at status.cloudcabin.com (opens in a new tab), and the same live status appears in the footer of every page of this site and in the client area, where each monitor shows its last 90 days.
We run our web hosting plans to a 99.99% uptime target. Our Refund Policy explains when service credits may be offered for prolonged disruption caused by Cloud Cabin.
Monitor your own site
You do not have to rely on your host's numbers. A free external monitor can check your site every one to five minutes and email you when it fails. Set it up on your main page and on anything that earns money, such as a checkout or booking form. If the monitor and your host disagree, you have the evidence to take to the support team.
Fast pages matter as well as available ones. LiteSpeed and NVMe storage help, and so does the basic hygiene that keeps a site from being taken down by an attack.
Frequently asked questions
It allows about 8 hours 46 minutes of downtime a year, or 43 minutes in a month. That is fine for a personal site and too much for a shop that sells around the clock. Choose the target that matches what an hour offline would cost you.
About 4 minutes 19 seconds in a 30-day month, or about 52 minutes 34 seconds over a year.
It depends on the provider's SLA. Many exclude announced maintenance from the calculation, so read the exclusions.
99.999% uptime, which allows about 5 minutes 15 seconds of downtime a year. It is a target for critical infrastructure, and rarely offered on shared hosting.
