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What is Availability?

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Availability is the percentage of time that a service or resource is fully available for its intended use. It is a key operating metric in a number of industries.


  1. The percentage of time that a service or resource is up.
  2. The percentage of time that a service or resource is available when it is expected to be available such as during business hours.
  3. The actual uptime of a resource as a percentage of its expected uptime.
  4. The uptime of a facility, infrastructure component, machine, device, service, product, function, system, business capability or process.


  1. It is common for availability to be calculated relative to 24/7/365 uptime. For example, an IT service with availability of 99.99% is down for less than 5 minutes a month.
  2. Services and resources that are only expected to be up during certain business hours are calculated against this business schedule.
  3. Some industries commonly exclude planned maintenance schedules from availability calculations.
Overview: Availability
Also Known As
Operational Availability
Related Concepts


This is the complete list of articles we have written about quality.
Conformance Quality
Cost Of Poor Quality
Credence Quality
Critical To Customer
Critical To Quality
Customer Satisfaction
Data Quality
Defect Density
Defect Rate
Defensive Design
Design Quality
Document Quality
Ease Of Use
Experience Quality
Figure Of Merit
Fit For Purpose
Information Quality
Non-Functional Testing
Operational Testing
Perceived Value
Planned Obsolescence
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Quality Assurance
Quality Control
Quality Culture
Quality Examples
Quality Improvement
Quality Management
Quality Metrics
Quality Objectives
Quality Of Life
Quality Policy
Quality Requirements
Quality Testing
Recovery Paradox
Regression Testing
Reliability Engineering
Service Quality
Types of Quality
Acceptance Testing
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