Mean Time Between Failures
Mean Time Between Failures, or MTBF, is the average operating time between failures of a repairable asset during a defined period.
What this term means in maintenance
Mean Time Between Failures, or MTBF, is the average operating time between failures of a repairable asset during a defined period.
MTBF formula
MTBF = Total operating time ÷ Number of failures
The operating time and failure count must cover the same asset population and reporting period.
Practical example
A repairable machine operates for 2,000 hours and experiences five failures.
MTBF = 2,000 ÷ 5 = 400 hours
The result means the machine operated for an average of 400 hours between recorded failures during that period.
What MTBF can show
MTBF can help compare reliability over time, identify deteriorating assets, and assess whether corrective actions are reducing repeat failures.
Important limitation
MTBF is an average. It does not predict the exact date of the next failure, and it can hide different failure modes or major variation between assets.
Common mistakes
Common errors include counting planned stops as failures, mixing calendar time with operating time, changing the definition of failure, or combining unrelated assets without a valid reason.
Related measures
MTTR describes average repair duration. Availability reflects the combined effect of reliability and downtime.
How this term differs
Mean Time Between Failures is average operating time between repairable-asset failures. It is related to Mean Time to Failure, Failure Rate, and Failure Frequency, but these terms describe different records, measures, roles, strategies, or decisions and should not be used interchangeably.
Related concepts
Related maintenance terms
Keep exploring connected CMMS, reliability, and maintenance planning terms.
Failure Rate
Failure rate is the number of failures observed per unit of operating time for an asset or defined equipment population.
Mean Time to Repair
Mean Time to Repair, or MTTR, is the average time required to restore a repairable asset after failure.
Equipment Reliability
Equipment reliability is the probability that an asset will perform its required function without failure for a defined time under stated operating conditions.
Mean Time Between Failures FAQs
- What is the MTBF formula?
MTBF equals total operating time divided by the number of failures during the same period.
- Is higher MTBF better?
A higher MTBF generally indicates longer average operation between failures, but the result must be interpreted with failure severity and operating context.
- Can MTBF predict the next failure date?
No. MTBF is a historical average and does not identify the exact timing of the next failure.