MTBF Calculator
Mean time between failures, or MTBF, is the average running time a machine or part works before it fails. Enter the total time it ran and how many times it failed in that time.
- Free
- Works offline after your first visit
- Saves on this device
- No sign-up
- Updated
How it works
MTBF is the total operating time divided by the number of failures. Count only the time the equipment was running, and count each failure once.
The result is an average for the group you measured. One unit may last far longer, or fail sooner, than the average.
Worked example
A unit that ran for 2,000 h with 4 failures has a mean time between failures of 500 h.
Questions
Does downtime count?
No. MTBF uses operating time only, so leave out time the equipment sat idle or was being repaired.
What unit does the answer use?
The answer shows in hours. Enter the running time in any time unit you like, and the tool converts it.
Is MTBF the same as lifespan?
No. Lifespan is how long one unit lasts overall. MTBF averages the running time between failures across a group.
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