MTBF and MTTR: Machine Reliability KPIs
Machine reliability determines how often your equipment runs without failure and how quickly it recovers when something goes wrong. Together, MTBF (Mean Time Between Failures) and MTTR (Mean Time To Repair) tell you how dependable your machines are, how prepared your maintenance team is, and how much of your availability pillar in OEE (Overall Equipment Effectiveness) is being lost to breakdowns.
Summarize with AI
What Are MTBF and MTTR?
| Metric | Definition | Formula | Goal |
|---|---|---|---|
| MTBF (Mean Time Between Failures) | The average time a machine operates between one breakdown and the next (considering only actual operating/uptime). | MTBF = Total Operating Time ÷ Number of Failures | High MTBF = fewer breakdowns |
| MTTR (Mean Time To Repair) | The average time it takes to repair a machine and return it to operation. | MTTR = Total Downtime ÷ Number of Failures | Low MTTR = faster recovery |
In short: A high MTBF means your machine rarely fails. A low MTTR means it recovers quickly when it does. These two figures give maintenance teams a simple but powerful way to track machine reliability and improve uptime.
MTBF and MTTR Formulas Explained
Let’s see how to calculate them with a practical example.
Example 1: Calculating MTBF
A packaging line operates (is actually running) for 400 hours and fails four times.
MTBF = 400 ÷ 4 = 100 hours
This means, on average, the line runs 100 hours between failures.
Example 2: Calculating MTTR
Those four failures caused 8 hours of total downtime.
MTTR = 8 ÷ 4 = 2 hours
On average, repairs take 2 hours each.
How they feed into availability
In OEE, availability is typically calculated as:
Availability = Operating Time ÷ Planned Production Time × 100%
Planned Production Time = time you intended to run.
Operating Time = Planned Production Time − all downtime (including breakdowns).
MTBF and MTTR also relate to availability through a classic reliability formula:
Availability = MTBF ÷ (MTBF + MTTR)
So if you can increase MTBF or decrease MTTR, availability rises — and so does your OEE score.
Why MTBF and MTTR Matter for OEE
Availability is one of the three pillars of OEE (the others being performance and quality). MTBF and MTTR directly determine how strong that pillar is.
When MTBF is low, breakdowns happen too often.
When MTTR is high, repairs take too long.
Both eat away at your available production time.
Example
If a machine has 80 hours of planned production time in a week and loses 8 hours to breakdowns spread across 4 failures:
Planned Production Time = 80 hours
Downtime from failures = 8 hours
Operating Time = 80 − 8 = 72 hours
Failures = 4
Then:
MTBF = Operating Time ÷ Number of Failures
MTBF = 72 ÷ 4 = 18 hours
MTTR = Total Downtime ÷ Number of Failures
MTTR = 8 ÷ 4 = 2 hours
OEE-style Availability = Operating Time ÷ Planned Production Time × 100%
Availability = 72 ÷ 80 × 100 = 90%
Reliability-style Availability (using MTBF and MTTR):
Availability = MTBF ÷ (MTBF + MTTR)
Availability = 18 ÷ (18 + 2) = 18 ÷ 20 = 0.9 = 90%
By significantly increasing MTBF (fewer failures) or reducing MTTR (faster repairs), you can raise availability into the 95–97% range, which can translate into thousands of additional products every month depending on your throughput.
Read next: Machine Availability – The Key to Improving OEE
How to Improve MTBF and MTTR
Improving reliability isn’t just about maintenance — it’s about information flow. Here are practical ways to improve both metrics. For reducing setup and changeover time specifically, apply SMED (Single-Minute Exchange of Die)
1. Implement Preventive and Predictive Maintenance
Preventive maintenance keeps machines from failing unexpectedly. Predictive maintenance takes it a step further — using sensor data to spot problems before they cause downtime.
With GlobalReader’s Maintenance app, you can:
Create recurring maintenance schedules
Receive notifications for upcoming jobs
Monitor the health of each device in real time
This reduces surprise failures (boosting MTBF) and shortens response times (lowering MTTR).
Read next: Preventive vs Predictive Maintenance Compared
2. Track Downtime Reasons in Real Time
Knowing that downtime happened isn’t enough — you need to know why.
With GlobalReader Operator (Shopfloor Feedback), operators log every interruption as it happens, including the reason. This creates a real-time record of all stops, which helps identify recurring faults and trends.
Typical downtime reasons include:
Mechanical or electrical failures
Waiting for parts or maintenance
Operator absence
Analysing this data reveals where improvements to MTBF and MTTR will have the biggest impact.
Read more: Planned vs Unplanned Downtime
3. Analyse Maintenance Data to Find Root Causes
Every failure leaves a trail of clues — in repair logs, sensor data, and operator notes. Analysing those records helps you identify patterns such as:
The same component failing repeatedly
Long waits for spare parts
Certain shifts reporting more breakdowns
Use a Kaizen approach (PDCA cycle) to test small changes, measure their impact on MTBF and MTTR, and standardise successful practices. With GlobalReader Analytics, you can visualise these trends in charts and dashboards, helping you target the most expensive reliability issues.
4. Reduce MTTR Through Better Planning and Communication
Quick recovery relies on good planning and clear communication.
Tips to shorten MTTR:
Keep critical spares in stock.
Use maintenance scheduling tools to assign technicians immediately.
Provide instant alerts when a machine stops.
Train operators to use Call for Help features quickly.
When everyone knows exactly what’s happening and when, downtime drops dramatically.
MTBF and MTTR in Practice: Turning Data into Action
Once you’re tracking MTBF and MTTR regularly, the next step is turning numbers into insight. Here’s how to interpret them:
High MTBF shows your maintenance strategy is effective.
Low MTBF signals recurring failures or neglected servicing.
High MTTR means your response or repair process is too slow.
Low MTTR means maintenance is well organised and supported.
Combining these metrics with real-time production tracking (via GlobalReader’s ecosystem) gives you a complete view of machine health and helps you make proactive, data-based decisions. When MTBF and MTTR improve, so do machine availability, OEE, and profitability.
Remember this about MTBF and MTTR
MTBF measures how long a machine runs between breakdowns (based on operating time).
MTTR measures how quickly it can be repaired.
Both metrics define machine reliability and strongly affect OEE availability.
Increasing MTBF and reducing MTTR boosts uptime, efficiency, and ROI.
Real-time monitoring tools like GlobalReader make it easier to track, analyse, and improve both metrics.
FAQ: MTBF and MTTR
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MTBF (Mean Time Between Failures) measures the average time a machine runs (while operating) before breaking down. A higher MTBF indicates greater reliability.
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MTTR (Mean Time To Repair) measures the average time it takes to fix a failure and restart production. A lower MTTR means faster recovery and higher availability.
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Both metrics affect the Availability part of OEE. Fewer breakdowns (high MTBF) and faster repairs (low MTTR) reduce downtime and increase OEE scores.
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Use preventive maintenance schedules, real-time downtime tracking, and data analytics. GlobalReader’s ecosystem connects all of these in one place so you can act quickly on reliability issues.
