Reliability and uptime
MTTR calculator
Mean Time To Repair is the average time it takes to restore a failed asset to service. It is a measure of how well your team responds, not of how reliable the equipment is.
MTTR = Total repair time ÷ Number of repairs
Summed across every repair in the period
Show the assumptions
- Formula
- MTTR = Total repair time ÷ Number of repairs
What you include in repair time changes the number substantially. State whether it covers diagnosis and parts waiting time, or hands-on wrench time only.
MTTR is where parts availability shows up. A team with fast diagnosis and no spare on the shelf reports a bad MTTR for a stores problem, which is why it is worth splitting the total into response, diagnosis, parts wait and repair.
MTTR
—
Prefilled with an example. Change any number and the result updates.
How to calculate MTTR
MTTR = Total repair time ÷ Number of repairs
What you include in repair time changes the number substantially. State whether it covers diagnosis and parts waiting time, or hands-on wrench time only.
Worked example
- Total repair time 21 hrs
- Number of repairs 7
MTTR = 3.0 hrs
Reading the result
MTTR is where parts availability shows up. A team with fast diagnosis and no spare on the shelf reports a bad MTTR for a stores problem, which is why it is worth splitting the total into response, diagnosis, parts wait and repair.
MTTR questions
Does MTTR include waiting for parts?
It depends which definition you are using, and that is exactly why you should say. Mean time to repair traditionally covers active repair time. Mean time to recovery, often abbreviated the same way, covers everything from failure to back in service, including parts waiting and administrative delay. The second is larger and usually the more honest figure to report to a plant manager.
Why is MTTR a time and not a percentage?
Because it measures duration. Any tool reporting MTTR with a % suffix is mislabeling it. The old UpKeep calculator did this, which is one of the reasons these pages were rebuilt.
How do MTTR and MTBF combine?
Inherent availability is MTBF ÷ (MTBF + MTTR). It is a useful sanity check: improving MTTR raises availability, but on an asset with a short MTBF you get more from stopping the failures than from fixing them faster.
Related calculators
Time repairs from the work order
UpKeep records the work, the hours and the failures this metric depends on, so MTTR is a report rather than a spreadsheet exercise.