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Glossary

MTBF vs MTTR

The two core reliability KPIs every maintenance engineer must know.

⏱️ MTBF

Mean Time Between Failures
Average operating time between two consecutive failures. Measures reliability.

🔧 MTTR

Mean Time to Repair
Average time to restore a failed asset. Measures maintainability.

MTBF Formula & Calculation

MTBF = Total Operating Time ÷ Number of Failures
MTBF = Total Operating Hours ÷ Number of Failures

Example: A CNC machine ran for 960 operating hours in a quarter and experienced 4 failures. MTBF = 960 ÷ 4 = 240 hours.

A higher MTBF is better — it means the equipment fails less frequently. Improving MTBF requires predictive and preventive maintenance strategies, better spare parts quality, and reduced operator-caused stoppages.

MTTR Formula & Calculation

MTTR = Total Repair Time ÷ Number of Repairs
MTTR = Total Repair Hours ÷ Number of Repairs

Example: The same CNC machine had 4 failures with repair durations of 45, 30, 60, and 25 minutes. Total repair time = 160 minutes. MTTR = 160 ÷ 4 = 40 minutes.

A lower MTTR is better — it means faster restoration of production capacity. MTTR is improved by better spare parts availability, standard repair procedures, skilled technicians, and clear fault diagnostics.

MTBF, MTTR & OEE Availability

These two KPIs directly feed the Availability component of OEE:

Availability = MTBF ÷ (MTBF + MTTR)

Using the example above: Availability = 240 ÷ (240 + 0.67) = 99.7% — but only for the time the machine was scheduled to run. OEE multiplies this with Performance and Quality to give the full picture.

Any unplanned downtime event is captured in both MTBF and MTTR tracking, and also appears as an OEE downtime event classified under one of the Six Big Losses.

Comparison: MTBF vs MTTR

AttributeMTBFMTTR
Full nameMean Time Between FailuresMean Time to Repair
MeasuresReliabilityMaintainability
GoalMaximise (longer = better)Minimise (shorter = better)
Improved byPredictive / preventive maintenance, better parts qualitySpares availability, SOPs, technician training
OEE impactRaises Availability (fewer failures)Raises Availability (faster recovery)
UnitsHours (or minutes)Hours (or minutes)

Improving MTBF and MTTR with Predictive Maintenance

The most effective way to simultaneously improve both metrics is predictive maintenance (PdM):

Shopfloor Copilot tracks equipment health scores (0–100), calculates predicted failure dates using Prophet time-series forecasting, and raises maintenance alerts ranked by criticality — all directly linked to your OEE dashboard.

Frequently Asked Questions

What is a good MTBF?
It depends entirely on the asset and industry. For critical production equipment, world-class plants target MTBF of hundreds to thousands of hours between failures. The key is tracking your baseline and improving it consistently — a 20% MTBF improvement is more meaningful than any absolute benchmark.
What is the difference between MTTR and MTTF?
MTTF (Mean Time to Failure) applies to non-repairable assets — it measures how long before an item fails and must be replaced entirely (e.g. a light bulb). MTTR applies to repairable assets and measures how long repair takes. MTBF = MTTF + MTTR for repairable systems.
How do I track MTBF and MTTR automatically?
By connecting your equipment to an OPC UA-enabled MES. The system receives live machine state signals (running/stopped/fault), automatically calculates downtime durations, and aggregates them into MTBF and MTTR figures per asset — no manual log entry needed.

Track MTBF & MTTR Automatically

Shopfloor Copilot calculates equipment health scores, predicts failure dates, and surfaces MTBF/MTTR trends from live OPC UA signal data — no manual logging required.

Explore Predictive Maintenance →