Mean Time to Failure (MTTF)

What Does Mean Time to Failure (MTTF) Mean?

Mean time to failure (MTTF) is the length of time a device or other product is expected to last in operation. MTTF is one of many ways to evaluate the reliability of pieces of hardware or other technology.


Techopedia Explains Mean Time to Failure (MTTF)

Mean time to failure is extremely similar to another related term, mean time between failures (MTBF). The difference between these terms is that while MTBF is used for products than that can be repaired and returned to use, MTTF is used for non-repairable products. When MTTF is used as a measure, repair is not an option.

As a metric, MTTF represents how long a product can reasonably be expected to perform in the field based on specific testing. It is important to note, however, that the mean time to failure metrics provided by companies regarding specific products or components may not have been collected by running one unit continuously until failure. Instead, MTTF data is often collected by running many units, even many thousands of units, for a specific number of hours.

One of the main situations where terms like MTTF are extremely important is when hardware pieces or other products are used in mission-critical systems. Here it becomes valuable to know about general reliability for these items. For non-repairable items, MTTF is a statistic that is of great interest to engineers and others assessing these pieces as parts of larger systems.


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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.