MTTR (Mean Time To Repair) measures maintainability: the average time it takes to repair an asset and return it to service. Lower MTTR means faster recovery from failures.
The MTTR formula
MTTR = Total Repair Time / Number of Repairs
Step by step
- Define the repair window. Decide what counts in repair time: detection, diagnosis, the fix and the return to service (be consistent).
- Add up repair time. Sum the total time spent repairing the asset over the period.
- Count the repairs. Count the number of repair events in the same period.
- Divide. MTTR = Total Repair Time / Number of Repairs.
A worked example
Over a month, a team spent 10 hours on repairs across 5 repair events:
| Step | Calculation | Result |
|---|---|---|
| Repair time | - | 10 h |
| Repairs | - | 5 |
| MTTR | 10 / 5 | 2 h |
Skip the spreadsheet
Open the MTBF / MTTR Calculator
Our free MTBF / MTTR Calculator does this live, with the benchmark overlay.
Common mistakes
- Only timing the wrench-time and ignoring waiting for parts or technicians.
- Counting planned maintenance as a repair.
- Changing what is included in repair time between periods, so the trend is meaningless.
MTTR FAQ
Is a lower MTTR better?
Yes. A lower MTTR means faster repair and return to service, so less downtime per failure.
What should MTTR include?
Be consistent. Many teams include detection, diagnosis, the physical repair and the return to service. Waiting for spares is a big, often hidden, part.
How does MTTR affect availability?
Lower MTTR raises availability, because each failure costs less downtime.
Related: MTBF · planned vs unplanned downtime · cost of downtime