Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
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Glossary · Maintenance and diagnostics

Mean time to repair (MTTR)

Also known as: MTTR, Mean repair time

German: Mittlere Reparaturzeit (MTTR)

In maintenance and reliability engineering, the mean time to repair (MTTR) is the average time needed to repair a failed item and return it to operation. Depending on the organization, it covers only the active repair or also diagnosis, waiting for parts and functional testing, so its definition must be stated.

  • Maintenance

In one sentence

MTTR, mean time to repair, is the average time needed to repair a failed item and return it to operation; its scope must be defined.

Example

Over the last year, the plant recorded an MTTR of 45 minutes for servo drive faults, mainly because spare drives were stocked next to the line.

How it applies

  • Engineering: Modular design, quick-release connectors, good diagnostics and clear labeling reduce repair time.
  • Maintenance: Plants track MTTR to find where time is lost, for example in diagnosis, spare part logistics or restart procedures.
  • Operation: Together with Mean time between failures (MTBF), MTTR determines availability; a common approximation is MTBF divided by the sum of MTBF and MTTR.
  • Documentation: Clear Troubleshooting instructions, correct spare part numbers and exchange procedures shorten repair time directly. When a contract or data sheet states an MTTR, the documentation should say which activities it includes.

Mean time to repair vs. mean time to restoration

The abbreviation MTTR is used for both. IEC 60050-192 defines MTTR as Mean time to restoration (MTTR), which covers the whole time until the item is restored, while the pure repair time is called mean repair time. Check which one a figure refers to before comparing values.

By knowledge.aitechdoc.world · Published September 26, 2026 · Last reviewed

Source: AI TechDoc Knowledge editorial definition, based on maintenance and reliability practice and IEC 60050-192

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Knowledge and are not part of any standard.

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