Uptime = (Total available time/total time per year) x 100
The total number of hours your website is available is divided by the total number of hours per year multiplied by 100. In other words, uptime is calculated based on the number of hours that your web hosting server is available during a given period of time.
Let’s take a look at an example. We know that there are 365 days per year so in terms of hours, there are a total of 365 x 24 = 8760 hours. And if there were 4 hours of downtime per year, then the calculation would be:
(8756 / 8760) x 100 = 99.95%