Mean Time to Failure Versus Mean Time Between Failure – KBA94271

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Question: What is the difference between Mean Time to Failure (MTTF) and Mean Time Between Failure (MTBF)?

 

Answer:

The MTTF is the average, or mean, of the amount of time that a design or component is in operational condition. The MTBF is the average time between failures, including the average repair time.

In a lot of designs and components, the MTTF value is very similar to the MTBF value with MTBF being slightly greater than MTTF. This is because MTBF includes the repair time of the designs or components. If a design or component works for an extended time, then it fails, is repaired in a reasonable amount of time, and then once again works for an extended time, the MTTF is the average, or mean, of the amount of time that it is in operational condition. The MTBF is the average time between failures including the average repair time.