MTBF (Mean Time Between Failures) is a statistical measure of device reliability, defined as the average operating time between failures under nominal conditions. Expressed in hours, it represents the expected reliability of large numbers of identical units, not a guaranteed lifetime of a single device. For example, MTBF = 50,000 h means that a large population of identical units accumulates, on average, 50,000 operating hours per failure – not that each unit will run for 50,000 hours.
MTBF is calculated from testing, simulation, or historical data and excludes extreme operating conditions such as high humidity, vibration, or extreme temperatures. Widely used in industrial, medical, and military sectors, MTBF – together with MTTF (Mean Time To Failure) and MTTR (Mean Time To Repair)—helps plan product lifecycle and service schedules.
