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MTBF Calculator

Mean operating time between repairable-system failures.

Inputs

Illustrative example values — replace them with data from your analysis period.

Results

Mean time between failures120 hours

A higher MTBF generally indicates longer average operating time between recorded failures; compare only equivalent assets and periods.

Formula and scope

MTBF = total operating time / number of failures. Use one consistent failure definition and observation boundary.

Results use only visible inputs. OEE thresholds are configurable references, never universal standards. Downtime costs are scenario estimates, not accounting measurements; avoid adding a cost already included in the unit value or contribution margin.

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Engineering reference

MTBF Calculator – Mean Time Between Failures

Calculate average operating time between recorded failures for a repairable asset or homogeneous fleet.

Calculation method

The engine divides total operating time by the number of failures, preserving the selected time unit.

Formulas used

  • MTBF = total operating time / number of failures

Worked example

Example: 720 operating hours and 6 failures gives an MTBF of 120 h.

How to interpret the result

A higher MTBF means longer average operation between recorded failures only when failure definition and scope remain unchanged.

Common mistakes

  • Using calendar time instead of operating time.
  • Changing the failure definition between periods.
  • Pooling unlike assets.

Scope and limitations

  • Use one consistent observation boundary and validated production or maintenance records.

Frequently asked questions

Is MTBF the expected life of a machine?

No. It is an average interval between failures for repairable systems, not service life.

Should planned stops count?

Not as failures; use actual operating time and a stable failure definition.

How is MTBF different from MTTR?

MTBF concerns time between failures; MTTR concerns average restoration duration.