Enter the total uptime (hours) and total downtime (hours) into the calculator to determine the % availability of a system.

## % Availability Formula

The following formula is used to calculate the percentage availability of a system.

A = UT / ( UT + DT ) *100
• Where A is the percentage availability (%)
• UT is the total uptime (hours)
• DT is the total downtime (hours)

To calculate an availability percentage, divide the total uptime by the sum of the uptime and downtime, then multiply by 100.

## Availability Definition

What is a percentage availability? A % availability is a ratio of the total time a system is running, known as uptime, and the total possible time a system could be running. The total time the system could potentially run is known as the sum of the uptime and downtime.

## Example Problem

How to calculate % availability?

1. First, determine the total uptime.

For this problem, we are looking at the total uptime and downtime of a web server over a month period. The total uptime is found to be 690 hours over the month.

2. Next, determine the total downtime.

The total downtime of the server was measured to be 30 hours last month.

3. Finally, calculate the percent availability.

Using the formula, the percent availability is found to be 690 / (690+30) *100 = 95.83%.