Mean Time to Repair
Mean Time to Repair (MTTR) is the average time required to diagnose and repair a failed asset and restore it to normal operating condition. MTTR measures maintenance efficiency by capturing the full repair cycle - from failure detection through diagnosis, parts procurement, repair execution, and verification. Lower MTTR means less downtime and faster recovery from equipment failures.
Key Points
- Measures the average duration of unplanned repair activities
- Includes diagnosis, parts sourcing, repair work, and testing
- Lower MTTR indicates more efficient maintenance operations
- Used alongside MTBF to calculate overall asset availability
- Directly impacts production uptime and operational costs
Formula
Example
Scenario: An HVAC unit experienced 6 failures over a year. The total time spent repairing it across all events was 18 hours.
Result: The HVAC unit has an MTTR of 3 hours, meaning each repair takes an average of 3 hours to complete.
MTTR Formula and Measurement
To calculate MTTR accurately, track the time from when a failure is reported or detected to when the asset is confirmed operational again. Include all phases of the repair process - initial response, diagnosis, waiting for parts, performing the repair, and post-repair testing. Some organizations distinguish between MTTR (time to repair) and MTTRS (time to restore service), where the latter includes administrative and logistical delays beyond the hands-on repair work.
MTTR vs MTBF
MTTR and MTBF are complementary metrics that together define asset availability. MTBF measures how long equipment runs between failures (reliability), while MTTR measures how quickly failures are resolved (maintainability). The relationship is expressed as Availability = MTBF / (MTBF + MTTR). An asset with high MTBF and low MTTR has excellent availability. Improving either metric increases uptime, but the most cost-effective strategy depends on whether failures are frequent (improve MTBF) or repairs are slow (reduce MTTR).
Reducing MTTR
- Spare parts inventory: Keep critical spares on-site to eliminate procurement delays
- Standardized procedures: Create step-by-step repair guides for common failure modes
- Technician training: Invest in skills development to speed diagnosis and repair
- Diagnostic tools: Use condition monitoring data to pre-diagnose issues before dispatching technicians
- Mobile CMMS access: Give technicians real-time access to manuals, history, and parts availability in the field
- Root cause documentation: Build a knowledge base of past repairs to accelerate future diagnosis
Tracking MTTR in CMMS
CMMS software automates MTTR tracking by capturing timestamps at each stage of the work order lifecycle - creation, assignment, in-progress, and completion. This eliminates manual time tracking and provides accurate, auditable repair duration data. Advanced CMMS platforms break MTTR into sub-components like response time, diagnostic time, parts wait time, and wrench time, enabling targeted improvements. Trending MTTR by asset, location, technician, or failure type reveals patterns that drive operational improvements.
Reduce MTTR with AssetLab Work Order Management
AssetLab provides the tools you need to put these concepts into practice with Canadian data residency and CAD pricing.