What this calculator does
B10 is a percentile life, not an average life. It uses t₀.₁ = η[-ln(0.9)]^(1/β), the Weibull inverse reliability equation at R = 0.90.
When to use it
Use B10 when setting early-life reliability requirements, preventive replacement discussion points, or supplier comparison criteria.
Inputs and formula
η is characteristic life and β is the distribution shape. Both must come from the same population and duty cycle; a fitted value with wide confidence bounds should be reported with those bounds.
Worked example and interpretation
For η = 1,000 hours and β = 2, B10 is about 325 hours. At that age, the model expects one failure in ten comparable units, not that every unit needs replacement.
Practical notes and limitations
Percentile life is sensitive to β. Avoid using B10 as an automatic replacement interval without consequence, inspection, and condition information. Read Understanding Weibull analysis and the Weibull parameter reference.