What Is Uptime?

Date First Published: 23rd April 2022

Topic: Computer Networking

Subtopic: Network Services

Computer Terms & Definitions

Difficulty Level: 2/10

Learn more about what uptime is in this article.

Uptime refers to the time period when a network or server is up and running. It is the opposite of downtime, which refers to the time period when a server goes down and is inaccessible. Uptime is often used to give a measure of the reliability of a web server. For example, a web hosting company may say that their servers have 99.5% uptime, which means that the servers have been down 0.5% of the time that they have been available.

Ideally, a web server should have 99.99% uptime, since downtime, even of only a few hours can have a significant impact on a business as they may be unable to access important information and it can cause loss of revenue, especially if the business sells products online. In order to increase uptime, multiple servers may be configured so that the other server takes over, in the event that the first server fails.

How To Calculate Uptime?

Uptime can be calculated using this formula:

Uptime = Available hours – unavailable hours

Then, active hours ÷ available hours

For example, if a web server has been available for 10 years and it had 90 hours of downtime over these 10 years, it would be calculated:

365 x 10 = 3650 (there are 365 days in a year)

3650 + 2 = 3652 (this is because two leap years would occur during ten years)

3652 x 24 = 87,648 available hours

87,648 – 90 unavailable hours = 87,558 active hours

87,558 active hours ÷ 87,648 available hours = 99.8973% uptime

Other Definitions

Uptime also measures the period of time that a computer has been running since it was booted. Every time the computer reboots or shuts down, the downtime resets. For example, if a computer was booted at 7:00 am and it was running until 3:00 pm, its uptime would be 8 hours.