Definition
Uptime is the total time an asset is actually performing its intended function: the complement of downtime within the total period under measurement. It is a straightforward, additive time count, distinct from availability, which expresses the same underlying reliability and maintainability performance as a ratio or percentage.
Key facts
- A straightforward time count (hours or a similar unit) not a ratio or percentage.
- The direct complement of downtime: uptime plus downtime equals the total period under measurement.
- The raw figure that availability is calculated from (uptime divided by total time), but uptime itself is not a percentage.
- Requires the same consistent start/stop event definitions as downtime to be comparable over time.
How is Uptime calculated?
Uptime measures the total elapsed time an asset was actually performing its intended function, using the same consistently applied stop and resume events used for downtime, so the two figures together account for the full period under measurement without overlap or gap.
What influences Uptime?
Uptime is a raw time count. Availability is the derived ratio, uptime divided by total time (uptime plus downtime), expressed as a percentage. The two describe the same underlying performance, but uptime is the absolute figure and availability is its relative, comparable expression.
FAQ
Frequently asked questions
Which time counts as uptime?
All time an asset is actually performing its intended function, the direct complement of downtime: the raw figure availability is calculated from as a percentage of total time.
Last reviewed: