What this calculator does
MTTF estimates average life to failure by dividing total accumulated service time by the observed failures in a non-repairable population. It is commonly used for components, consumables, and units replaced rather than repaired.
When to use it
Use MTTF for consistent units under comparable duty. It is not interchangeable with MTBF: a repairable system can experience repeated failures while a non-repairable unit reaches one terminal failure.
Inputs and formula
Use a common clock such as operating hours, cycles, or starts. MTTF = total operating time ÷ units failed
Worked example and interpretation
5,000 unit-hours with 25 failed units produces an MTTF of 200 hours. This mean does not identify the 10th-percentile life or capture wear-out shape.
Practical notes and limitations
Censored units that have not failed still contribute exposure but require proper life-data treatment for rigorous analysis. If failure behavior changes with age, duty, or environment, use a Weibull or survival analysis instead of assuming a single mean explains the risk.