MTTR is the average time required to repair a failed asset and return it to operational status. It is calculated by dividing total repair time by the number of repair events over a given period.
The Three Definitions
MTTR is used with three slightly different meanings depending on context:
Mean Time To Repair — the time from when a technician begins working on a failed asset to when the asset is restored to function. This is the standard definition in maintenance operations and the most useful for measuring technician efficiency and diagnostic speed.
Mean Time To Restore — a broader measure that includes the full downtime period: from when the failure was detected (not just when repair began) to when the system is back in service. This includes dispatch time, waiting for parts, and post-repair testing. More useful for measuring operational impact than repair-team performance.
Mean Time To Resolve — primarily used in IT service management; the elapsed time from incident report to full ticket closure, including follow-up verification. Rarely used in physical maintenance contexts.
In physical maintenance management, Mean Time To Repair is the standard. Unless otherwise specified, MTTR in a maintenance context refers to this definition.
The Formula
MTTR = Total Repair Time / Number of Repairs
Example: Four repairs in one month, taking 2, 4, 1.5, and 3.5 hours respectively. Total repair time = 11 hours. Number of repairs = 4. MTTR = 11 / 4 = 2.75 hours
What MTTR Measures and Why Teams Track It
MTTR is a measure of maintainability — how efficiently a team can recover from a failure. A lower MTTR indicates faster diagnosis, better access to parts, clearer procedures, and more skilled technicians. A higher MTTR points to inefficiencies in one or more of those areas.
Tracked over time, MTTR reveals trends: whether repair efficiency is improving, which assets or failure types take disproportionately long to fix, and whether specific teams or locations are slower than others on comparable work.
Why It Matters in Maintenance
MTTR directly affects equipment availability. Paired with MTBF (how often failures occur), it determines the percentage of time an asset is operational. A maintenance operation that improves MTTR — through better procedures, stocked parts, and skilled technicians — reduces the operational cost of every failure event.
Related Terms
Full guide: How to Calculate MTTR