MTBF

MTBF (Mean Time Between Failures) is the average operating time between two failures for a repairable asset. The unit is typically hours or number of cycles. It is one of the core reliability engineering metrics, feeding into preventive maintenance frequency, spare-part inventory, warranty period, and total maintenance cost calculations. For non-repairable items the equivalent is MTTF (Mean Time To Failure). Practical computation: total operating time over a given period divided by the number of failures. High MTBF means a reliable asset; low MTBF means frequent failures. But because MTBF is an average, it doesn't mean an asset will fail at exactly X hours — it is interpreted under a Weibull or similar probability distribution.