MTTR most often stands for mean time to repair: the average time it takes to get a failed asset working again. It measures maintainability, the counterpart of the reliability measured by MTBF. The basic formula divides the total repair time by the number of repairs in the same period.
MTTR full form: four different meanings
The same four letters are used for different measures, especially between maintenance and IT. Check which one a report uses before comparing figures.
| Full form | Clock starts | Clock stops | Common in |
|---|---|---|---|
| Mean time to repair | Repair work starts (or the failure is reported, by some definitions) | Asset is repaired and tested | Maintenance, manufacturing |
| Mean time to recovery / restore (restoration) | Failure or outage begins | Service is back for users | IT operations, utilities, facilities |
| Mean time to respond | Alert or report is raised | Someone starts working on it | Help desks, security, field service |
| Mean time to resolve | Issue is reported | Cause is fixed and the issue is closed, including follow-up | IT service management |
Mean time to restoration is close to what many maintenance teams actually need: the whole period the asset is unavailable, including waiting for a technician and parts, not just hands-on repair. Write your definition down, for example "from work order created to asset back in service", and apply it to every job.
How to calculate MTTR: a worked example
A packaging site records four corrective repairs on its filling machines last quarter (illustrative figures, in hours):
| Work order | Waiting for technician | Diagnosis and repair | Waiting for parts | Test and restart | Total downtime |
|---|---|---|---|---|---|
| WO-01 | 0.5 | 1.5 | 0 | 0.5 | 2.5 |
| WO-02 | 1.0 | 2.0 | 3.0 | 0.5 | 6.5 |
| WO-03 | 0.5 | 1.0 | 0 | 0.5 | 2.0 |
| WO-04 | 0.5 | 1.5 | 0 | 1.0 | 3.0 |
| Total | 2.5 | 6.0 | 3.0 | 2.5 | 14.0 |
The breakdown shows where the time goes. Three of the 14 hours were one job waiting for parts. Stocking that spare would have cut mean time to restore from 3.5 to 2.75 hours: (14.0 − 3.0) ÷ 4.
MTTR, MTBF and availability
MTBF tells you how often an asset fails; MTTR tells you how long each failure lasts. Together they give inherent availability:
Every hour of MTTR is an hour of downtime. To put a cost on it, multiply the hours lost by your cost per hour of downtime, or use the free downtime cost calculator.
How to reduce MTTR
- Stock critical spares, chosen from failure history.
- Make assets easy to find and identify: tags, accurate locations and the service history one scan away.
- Write repair procedures for common failures and keep manuals on the asset record.
- Respond faster with clear priorities and an on-call rota for critical assets.
- Train for diagnosis. Finding the fault can take longer than fixing it.
Common mistakes
- Mixing definitions, such as comparing your mean time to repair with a supplier's mean time to restore.
- Leaving out waiting time, which hides the easiest improvements.
- Including planned maintenance jobs. They are not failures and pull the average down.
- Averaging very few repairs. One long job distorts the figure, so look at the longest jobs and the median too.
Spreadsheet vs CMMS
You can calculate MTTR in Excel or Google Sheets from a list of repairs with start and end times: duration = end − start, then =AVERAGE() over the durations. It breaks down when times are typed in from memory, when "start" and "end" mean different things to different people, and when some jobs are never logged. Work orders with system-stamped times give consistent data for a corrective maintenance history.
MTTR in Asetavo
Asetavo work orders (Business plan) record when each job was started and completed, stamped by the server as the status changes, together with downtime minutes and parts and labour cost. You can export the work-order history to Excel or CSV and calculate MTTR as above. Built-in MTTR and maintenance KPI dashboards are on the roadmap. See Asetavo maintenance.
