Mean Time to Repair
Mean Time to Repair, or MTTR, is the average time required to restore a repairable asset after failure.
What this term means in maintenance
Mean Time to Repair, or MTTR, is the average time required to restore a repairable asset after failure.
MTTR formula
MTTR = Total repair downtime ÷ Number of repairs
The organization should define the start and end points consistently. Depending on the purpose, repair downtime may include diagnosis, waiting, repair, testing, and return to service.
Practical example
A machine has 600 minutes of repair downtime across 15 repair events.
MTTR = 600 ÷ 15 = 40 minutes
What MTTR can reveal
A rising MTTR may indicate difficult diagnosis, poor access, missing tools, unavailable parts, unclear instructions, insufficient skills, or long approval and isolation delays.
Important limitation
A low MTTR is not automatically good if temporary repairs are being used or work quality is poor. Repair speed must be balanced with safety, quality, and recurrence prevention.
Common mistakes
Do not mix different definitions of downtime, include planned maintenance without intending to, or compare assets with very different repair complexity without context.
How this term differs
Mean Time to Repair is the average active time required to repair failed equipment. It is related to Mean Time to Restore, but these terms describe different records, measures, roles, strategies, or decisions and should not be used interchangeably.
Related concepts
Related maintenance terms
Keep exploring connected CMMS, reliability, and maintenance planning terms.
Mean Time Between Failures
Mean Time Between Failures, or MTBF, is the average operating time between failures of a repairable asset during a defined period.
Equipment Downtime
Equipment downtime is the period when an asset is required or scheduled to operate but is unavailable or unable to perform its intended function.
Breakdown Maintenance
Breakdown maintenance is repair work performed after an asset has failed and can no longer perform its required function.
Glossary FAQs
- What is the MTTR formula?
MTTR equals total repair downtime divided by the number of repair events.
- Should MTTR include waiting for parts?
It can, depending on the chosen definition. The organization must consistently define the start and end of repair downtime.
- How can MTTR be reduced?
Improve diagnosis, job plans, access, skills, tools, spare-parts availability, approvals, isolation, and testing procedures.