Calculate Mean Time Between Failures
Enter your operating time, failure count, and repair hours to measure equipment reliability. See MTBF, MTTR, availability, and failure rate instantly.
Operating Data
Total time the equipment was in operation (excluding scheduled downtime)
Total number of unplanned equipment failures during the period
Total time spent repairing equipment across all failures
MTBF = 2000 hrs / 5 failures = 400.0 hrs
MTTR = 40 hrs / 5 failures = 8.0 hrs
Availability
98.0%
Excellent
MTBF
400.0
hours
MTTR
8.0
hours
Failure Rate
2.50
per 1,000 hours
MTBF : MTTR
50.0
ratio
Availability Breakdown
97%+
Excellent
90-97%
Good
80-90%
Fair
<80%
Needs Work
MTBF and MTTR Formulas
MTBF and MTTR are the two foundational metrics for measuring equipment reliability and maintenance performance. Together they determine equipment availability.
MTBF = Total Operating Time / Number of Failures
MTTR = Total Repair Time / Number of Failures
Availability = MTBF / (MTBF + MTTR)
Worked Example
A CNC machine runs for 2,000 hours over a quarter. During that period it experiences 5 unplanned breakdowns with a total repair time of 40 hours.
MTBF
400 hours
On average, the machine runs 400 hours between failures.
2,000 / 5 = 400 hrs
MTTR
8 hours
Each repair takes an average of 8 hours to complete.
40 / 5 = 8 hrs
Availability
98.0%
Equipment is available 98% of the time.
400 / (400 + 8) = 98.0%
Failure Rate
2.5 per 1,000 hrs
Expect about 2.5 failures every 1,000 operating hours.
(5 / 2,000) x 1,000 = 2.5
MTBF vs MTTR: What Each Metric Tells You
MTBF measures how often equipment fails. MTTR measures how quickly you recover. Both matter, but they drive different improvement strategies.
A higher MTBF means fewer breakdowns. Improving MTBF requires preventive maintenance programs, root cause analysis of failures, upgrading wear components, and better operating procedures. Focus on MTBF when failures are frequent and unpredictable.
A lower MTTR means faster recovery from failures. Improving MTTR requires spare parts availability, trained maintenance technicians, standardized repair procedures, and good diagnostic tools. Focus on MTTR when repairs are taking too long.
Availability is the outcome of both MTBF and MTTR working together. A machine with MTBF of 500 hours and MTTR of 2 hours achieves 99.6% availability. The same MTBF with MTTR of 50 hours drops to 90.9%. Both levers matter.
MTBF Benchmarks by Equipment Type
Reliability targets vary widely by equipment type, age, and operating conditions. These benchmarks provide a general reference for setting improvement goals.
| Equipment Type | Typical MTBF | Target MTTR | Target Availability |
|---|---|---|---|
| CNC Machines | 300-600 hrs | 4-8 hrs | 95-98% |
| Injection Molding | 400-800 hrs | 2-6 hrs | 96-99% |
| Packaging Lines | 100-300 hrs | 1-3 hrs | 90-96% |
| Conveyor Systems | 1,000-3,000 hrs | 2-4 hrs | 99%+ |
| Welding Robots | 500-1,500 hrs | 2-6 hrs | 97-99% |
These figures assume well-maintained equipment in normal operating conditions. Older machines or harsh environments will typically see lower MTBF values. Track your own baseline first, then set incremental improvement targets rather than chasing an industry number.