Glossary
What is MTBF?
MTBF (mean time between failure) is the average time between failures of an asset or system over a period. It is calculated as total operating time divided by the number of failures. Higher MTBF generally indicates better reliability.
What it means
MTBF is a common reliability KPI. It is used to compare assets, track trends and plan maintenance or replacement.
Why it matters
- MTBF = total operating time ÷ number of failures.
- Usually expressed in hours. Higher MTBF = more reliable.
- Requires consistent recording of failures (e.g. in work orders).
- Often used alongside MTTR to understand reliability and maintainability.
Example in maintenance operations
A pump runs 8,760 hours in a year and fails twice. MTBF = 8,760 ÷ 2 = 4,380 hours. A fleet vehicle travels 50,000 km before its first failure; that can be expressed as MTBF in kilometres for that period.
Related concepts
Frequently asked questions
What is the difference between MTBF and MTTR?
MTBF is the average time between failures (how often it fails). MTTR is the average time to repair after a failure (how long it takes to fix). Both are used to measure reliability and maintenance performance.
How do you calculate MTBF?
MTBF = total operating time of the asset (or population) divided by the number of failures in that period. You need clear definitions of 'failure' and consistent work order or incident data.
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