As you probably already know, server uptime is the amount of time that a server is up – or functioning and running smoothly – during any given period of time. With your web host, this translates to the amount of time that their servers are up, hence the amount of time that your website is up, running, and accessible.

You’re probably also already aware that web hosts display uptime as percentages, with many of them boasting and in some cases guaranteeing 99.9% uptime. But did you ever wonder exactly what these uptime percentages mean? Ever been curious about how you can calculate your own website uptime percentage?

Well, today you’re in luck. We’ll be taking a look at the numbers behind website uptime. So, hunker down and break out your calculators – this might get a bit tricky!

Calculating Your Website’s Uptime: The Hard Way

In order to calculate your website’s uptime, you’ll need to know either your estimated uptime or your estimated downtime for a certain period of time. Since most web hosts calculate their uptime percentages on a monthly basis, we’ll use 30 days for our example.

Now for the number crunching…

Let’s say that Ima Webmaster has a website that experienced an hour and a half of downtime during one month. If you recall your middle school math, you’ll know that we first need to convert all measurements to the same units to calculate Ima’s uptime.

30 days x 24 hours x 60 minutes = 43,200 minutes of total time (T)

1.5 hours x 60 minutes = 90 minutes of downtime (D)

43,200 minutes – 90 minutes = 43,110 minutes of uptime (U)

You can then use a simple formula to calculate Ima’s uptime percentage, like so:

(U / T) x 100 = Uptime Percentage (P)

From there, you can plug in the numbers:

(43,110 / 43,200) x 100 = 99.792%

By using this method, we’re able to calculate Ima’s website uptime percentage as roughly 99.8%, which isn’t terrible… but isn’t spectacular, either.

Let’s consider for a moment, though, that Ima is contemplating switching to a web host that guarantees a 99.9% uptime. How would we calculate the amount of time that her website could be down in any given month? In order to do this, we’ll need to multiply the total amount of time by the percentage of possible downtime, and divide that by 100. In this case, the percent of possible downtime can be calculated by subtracting the guaranteed uptime of 99.9% from the total possible uptime of 100%, which gives us 0.1% of possible downtime.

(43,200 x 0.1%) / 100 = 43.2 minutes of possible downtime each month

So, in Ima’s situation, switching to the host with a 99.9% uptime guarantee could reduce her website’s possible downtime by 46.8 minutes, potentially cutting it roughly in half.

Calculating Your Website’s Uptime: The Easy Way

Face it – calculating your website’s uptime the hard way involves entirely too much math and number crunching for the majority of us. Thankfully, with all of the tools and services out there these days, monitoring your website’s downtime doesn’t have to cause you a migraine.

Services like SiteUptime do the monitoring and calculating for you, making it an essential “set it and forget it” website tool  to which you only need to give an occasional thought. This leaves you more time to conquer other tasks, like creating killer content and getting noticed by Big G. One less thing to worry about – now you can get back to business.