99.9% uptime means your website can be down for up to 0.1% of the time. That is about 43 minutes a month (in a 30-day month), 10 minutes a week or 8 hours 45 minutes a year. It sounds almost perfect, but it still allows a 40-minute outage every month. Many guarantees, like AWS’s, are measured monthly, so a single hour-long outage would break a 99.9% promise for that month.
This guide turns every common uptime percentage into real minutes and hours, explains what a hosting “uptime guarantee” actually promises (usually a credit, not a refund), and shows how to check your own uptime.
Uptime percentages in minutes and hours
| Uptime | Allowed downtime per day | Per week | Per 30-day month | Per year |
|---|---|---|---|---|
| 99% | 14 min 24 s | 1 h 40 min 48 s | 7 h 12 min | 3 days 15 h 36 min |
| 99.5% | 7 min 12 s | 50 min 24 s | 3 h 36 min | 1 day 19 h 48 min |
| 99.9% | 1 min 26 s | 10 min 5 s | 43 min 12 s | 8 h 45 min 36 s |
| 99.95% | 43 s | 5 min 2 s | 21 min 36 s | 4 h 22 min 48 s |
| 99.99% | 8.6 s | 1 min | 4 min 19 s | 52 min 34 s |
| 99.999% | 0.9 s | 6 s | 26 s | 5 min 15 s |
How to work it out yourself
Take the downtime share and multiply it by the period. For 99.9%, the downtime share is 100% – 99.9% = 0.1%, or 0.001.
- Month: 30 days x 24 hours x 60 minutes = 43,200 minutes. 43,200 x 0.001 = 43.2 minutes.
- Year: 365 x 24 = 8,760 hours. 8,760 x 0.001 = 8.76 hours (8 hours 45.6 minutes).
99.9% vs 99.99%: is the extra 9 worth it?
Each extra “9” cuts the allowed downtime by 10 times. 99.9% allows about 43 minutes a month; 99.99% allows about 4 minutes. For a blog or small business site, 99.9% is usually enough. A shop that loses sales every minute it is offline may want a plan, or a setup with backups and failover, that targets 99.95% or higher.
What an uptime guarantee really promises
An uptime guarantee is a promise in a service level agreement (SLA). It usually doesn’t promise your site will never go down. It promises a partial credit on your bill if the host misses the target. Amazon’s EC2 SLA is a clear public example:
- The target is a monthly uptime of at least 99.99% per region.
- If uptime falls below that but stays at 99.0% or more, the credit is 10% of that month’s charge; between 95.0% and 99.0% it is 30%; below 95.0% it is 100%.
- To get a region-level credit, you must submit a claim through the AWS Support Center. (AWS also has a separate instance-level SLA whose hourly credit is applied automatically.)
- Outages caused by things outside Amazon’s reasonable control are excluded.
Shared hosting plans work the same way in principle, but the details differ by company and by product. Hostinger’s terms of service, for example, say the uptime guarantee for a service, if there is one, “is defined in other documents”, such as that service’s own agreement. So always read the SLA for the exact plan you buy, and check:
- What counts as “down” (the whole server, or just your site?)
- Whether planned maintenance is excluded
- What you get back (usually a credit for future bills, not cash)
- How to claim it, and the deadline
How to check your website’s real uptime
- Use an outside monitor. An uptime-monitoring service checks your site every few minutes from servers elsewhere and emails you when it fails. Your host’s own status page only shows problems the host knows about.
- Check often enough. A 5-minute check can miss short outages. A 1-minute check catches more, though some services only offer it on paid plans.
- Keep a monthly record. If you ever need to claim an SLA credit, your own log of outage times is your evidence.
- Compare with your host’s status page after every outage.
Some “downtime” isn’t the host’s fault: an expired domain, a broken plugin or a DNS mistake can all take a site offline. If your site goes down right after you change DNS settings, our guide to how long DNS propagation takes explains the wait.
Comparing hosts? See our Hostinger review, Hostinger vs Bluehost, Hostinger alternatives and what web hosting is.
Frequently asked questions
How much downtime is 99.9% uptime per month?
About 43 minutes 12 seconds in a 30-day month, or about 44 minutes 38 seconds in a 31-day month.
How much downtime is 99.9% uptime per year?
About 8 hours 45 minutes (8 h 45 min 36 s) in a 365-day year.
Is 99.9% uptime good for a website?
Yes, for most blogs and small business sites. Sites that lose money every minute offline may want 99.95% or higher.
What does 99.99% uptime mean?
Up to about 4 minutes 19 seconds of downtime in a 30-day month, or about 52 minutes a year.
Do I get a refund if my host misses its uptime guarantee?
Usually you get a credit on future bills, not a cash refund, and you often have to claim it. Check your plan’s SLA for the exact rules.
Does an uptime guarantee include maintenance?
Often not. Some SLAs leave out scheduled maintenance, sometimes only when you were warned in advance, and many exclude problems outside the host’s control. Read your plan’s agreement to see exactly what counts as downtime.
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