Web hosting providers offer a certain percentage of guaranteed uptime, or the amount of time per month that you can expect the server your site is on to be running. In the competitive world of hosting, this usually runs in the neighborhood of 99.5% and up, but what does this actually mean and should you worry about it?

If you take the total number of minutes in a month, 44640, and divide by the potential downtime of the hosting company, you will find how much you can expect your site to be down. If your host says 99.5% guaranteed uptime, then multiply the number of minutes in a month by .005 and you'll get 223 minutes per month, or about 3 and 3/4 hours of downtime per month that your site will be unavailable. This is generally for such things as rebooting, upgrades, etc.

That seems like a lot, but it depends on what you need your site for. If it's for critical customer orders, then you would want to look for a host that provides a better uptime guarantee, such as 99.9% or more. Or go for a dedicated server which would essentially mean 0% downtime.

But also keep in mind that the actual downtime will probably not be anywhere near that much; you may go months and months without any downtime at all. All the guaranteed uptime means is the maximum amount per month the host can take your site offline.