Mean Time to Repair or Mean Time to Recovery (MTTR) is the average time needed to return a faulty component or system to its proper operation. In making this prediction, the system’s maintainability, or the length of time for repair and maintenance in the event of system failure, is analyzed.

MTTR is also a factor in other reliability and maintainability forecasts and analyses. It can help calculate a product or system’s availability, the probability of an item being operable at any given time. This is based on a formula involving the Mean Time between Failures (MTBF) and the MTTR.

MTTR can range from a few milliseconds (in the event of a glitch in an Uninterrupted Power Supply or UPS) to hours or days (in application software or various complex machineries).

The duration of the component or system/s return to normal operation includes the diagnosis period and resolution of the problem. MTTR may decrease significantly if the failure rate is documented and predictable. Conversely, if the circumstances surrounding the system failure are unforeseen, the diagnosis will require a longer period of time. Inaccurate analyses may result to further disrepair, and thus extend the period before recovery. Factors such as these add to an increase in system MTTR.

If a maintenance contract includes MTTR, a shorter MTTR logically entails a larger cost because the provider ensures system restoration within a shorter span of time. The buyer or user pays a larger amount for quicker turnover.

MTTR has an immense bearing on the overall stability and the efficient operation of systems and businesses. System maintainability is an integral part to the operation of various industries, such as aeronautics or software production. Also, system reliability concerns the users as well as the manufacturers of a system. These are some of the reasons major businesses and international corporations rely heavily on MTTR.