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MTTR (Mean Time To Repair)

The average time required to restore equipment to operational status after an unplanned failure — a measure of maintenance effectiveness.

Formula

Total Repair Time ÷ Number of Repairs

Benchmarks

World-class: Consistently meeting planned repair times Good: Trending downward Typical: Stable but with outliers Poor: Increasing or highly variable

What Is MTTR?

Mean Time To Repair measures how quickly your maintenance team can get equipment back into production after an unplanned failure. Lower MTTR means less downtime per incident.

The Formula

MTTR = Total Repair Time ÷ Number of Repairs

Example: Five repairs in a month with repair times of 2, 3, 1.5, 4, and 2.5 hours. Total = 13 hours. MTTR = 13 ÷ 5 = 2.6 hours.

Typical Values

Repair TypeTypical MTTR
Mechanical adjustments0.5–2 hours
Component replacement2–8 hours
Major repairs8–48+ hours

Data Requirements

SourceRequiredWhat You Need
Machine DataYesDowntime start/end timestamps, downtime reason codes
CMMSOptionalWork order completion data (enhances analysis)

MTTR is a Phase 2 metric — it requires Unplanned Downtime tracking with reason codes.

Why It Matters

  • Measures maintenance effectiveness — how quickly your team responds to and resolves failures
  • Identifies training needs — technicians consistently slow on certain repair types need targeted support
  • Highlights parts availability issues — long MTTR often indicates spare parts stockouts
  • Guides spare parts strategy — stock critical spares for high-frequency, long-repair-time failures
  • Improves resource planning — realistic MTTR data enables better maintenance staffing decisions

Common Pitfalls

  • Not starting the clock at failure — MTTR should include the full time from failure to production, not just “wrench time”
  • Including time waiting for parts without tracking it separately — this hides the root cause
  • Not distinguishing diagnosis time from actual repair time — these require different interventions
  • Averaging repairs of vastly different scope — categorise by repair type for meaningful averages

Best Practices

  • Define clear start and stop points for repair time measurement
  • Track diagnosis time separately from fix time — if diagnosis is the bottleneck, the solution is different from when physical repair is slow
  • Categorise repairs by type for meaningful averages
  • Investigate outliers — both very long and unexpectedly short repairs warrant attention
  • Document repair procedures to reduce MTTR over time through standardisation
  • Use MTTR data to prioritise reliability improvements: high-frequency, high-MTTR repairs first

Strategic Use

  • Prioritise improvements: High MTTR + High frequency = top priority for reliability investment
  • Stock critical spares for repairs with historically long MTTR
  • Calculate maintenance staffing needs based on MTTR and failure rates from MTBF
  • Include MTTR in equipment selection criteria — easier to repair means lower total cost of ownership
  • MTBF — together with MTTR, gives a complete reliability picture
  • Uptime Percentage — the outcome MTBF and MTTR produce
  • Unplanned Downtime — the total downtime impact
  • OEE — MTTR affects the Availability component