When picking a web host it is very important to keep “uptime” in mind. What is “uptime” you ask? Simply put, uptime is the percentage to time that the website is “up,” measured annually. In other words, if your web host tells you they have an “uptime guarantee” of 99.999%, they say your website should be up and running 99.999% of the time. At least, that’s what you’d think it means.
Some web hosts don’t measure site uptime, but server uptime, or network uptime. It’s much easier to keep a network up than it is a server, and easier to keep a server up than a website. So make sure to clarify what “uptime” it is they’re talking about.
But what does that equate to in terms of “downtime” that you should expect? Is a 99.999% uptime guarantee really that much better than a 99.9% uptime guarantee? Let’s look at the numbers, shall we?
| Uptime Guarantee | Downtime Per Year |
|---|---|
| 99.999% | 5.256 minutes |
| 99.990% | 52.56 minutes |
| 99.900% | 8.76 hours |
| 99.800% | 17.52 hours |
| 99.500% | 1.825 days |
| 99.000% | 3.650 days |
| 95.000% | 18.250 days |
| 90.000% | 1.216 months |
| 85.000% | 1.825 months |
| 80.000% | 2.433 months |
A site with 99.9% uptime will be down 100 times longer per year than a site with 99.999% uptime. That equates to almost 9 hours down per year, as compared to just over 5 minutes per year, respectively.
