Maintenance & Reliability worked example

Weibull Life Estimate with characteristic life, eta of 9,000 hr: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop characteristic life, eta to 9,000 hr, then walk the calculation through step by step. Estimate a simplified Weibull B-life by multiplying characteristic life by shape, percentile, and duty factors.

The inputs for this scenario

  • Characteristic life, eta: 9,000 hr (the input this scenario stresses; the baseline uses 18,000)
  • Shape adjustment factor: 0.92 x (held at the documented default)
  • Target percentile factor: 0.7 x (held at the documented default)
  • Duty factor: 1 x (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Base percentile life = characteristic life, eta × shape adjustment factor × target percentile factor.
  • Weibull Life Estimate works out to 5,796 hr at these inputs, and this is the headline figure for the scenario.
  • Base Percentile Life works out to 5,796 hr at these inputs.
  • Duty Factor works out to 1 x at these inputs.
  • Eta Times Shape Adjustment works out to 8,280 value at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where characteristic life, eta sits at 18,000 hr and the headline result is 11,592 hr, this scenario comes in 50% below the baseline at 5,796 hr.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to characteristic life, eta, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. It uses simplified multiplicative factors rather than the exact Weibull inverse-CDF, so for safety-critical parts confirm the interval against a full reliability model and field data.

Results at a glance

  • Weibull Life Estimate: 5,796 hr (headline result)
  • Base Percentile Life: 5,796 hr
  • Duty Factor: 1 x
  • Eta Times Shape Adjustment: 8,280 value

Run it with your numbers

  • To rerun this with your own numbers, open the live Weibull Life Estimate calculator, set characteristic life, eta to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.