Maintenance & Reliability worked example

MTBF with total operating hours of 18,000 hr: a worked example

Push total operating hours up to 18,000 hr and the picture changes. This example computes every intermediate figure at that operating point. Use it to trend reliability, compare similar assets, or verify whether defect elimination is reducing failure frequency.

The inputs for this scenario

  • Total operating hours: 18,000 hr (raised for this scenario; the documented default is 7,200)
  • Number of failures: 12 failures (unchanged)
  • Normalization factor: 1 x (unchanged)

Working through the calculation

  • Applying the documented formula (MTBF = total operating hours รท number of failures) to the inputs above produces each figure below.
  • At this operating point the engine returns 1,500 hr / failure for mtbf, the number this scenario is built around.
  • At this operating point the engine returns 1,500 hr / failure for base hours per failure.
  • At this operating point the engine returns 1 x for normalization factor.
  • At this operating point the engine returns 12 value for failure count.

How this compares with the baseline

  • Against the tool's baseline example, where total operating hours sits at 7,200 hr and the headline result is 600 hr / failure, this scenario comes in 150% above the baseline at 1,500 hr / failure.
  • It divides total operating hours by the number of failures to give average hours between failures, then applies a normalization factor for comparison. The value of this scenario is the size of the gap it exposes: that gap, priced out over a year, is the budget you can justify spending to close it.

Results at a glance

  • MTBF: 1,500 hr / failure (headline result)
  • Base Hours per Failure: 1,500 hr / failure
  • Normalization Factor: 1 x
  • Failure Count: 12 value

Run it with your numbers

  • Every input above is editable in the live MTBF calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.