CALCULATORS / RELIABILITY AND ENGINEERING STATISTICS

Weibull life and reliability calculator

Two-parameter Weibull survival with supplied shape/scale; no fitting.

reliability-weibull.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	survival
	0.960789
	0.974725

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

survival target0.96 ✓ passes

BASELINE INPUTS

time1000 hscale5000 hshape2

CALCULATED

survival0.96079

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Weibull life and reliability
# Scope: Two-parameter Weibull survival with supplied shape/scale; no fitting.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

time = 1000 h
scale = 5000 h
shape = 2

survival := exp(-(time/scale)^shape)

check survival target: survival >= 0.95

scenario alternative: time = 800 h

Calculated from your source · not saved

Baseline · Baseline

survival target0.96 ✓ passes

alternative · alternative

survival target0.97 ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

survival: survival = exp(-(time/scale)^shape)

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

time: 1000 h
scale: 5000 h
shape: 2

Calculated

survival: 0.960789

Assumptions and limits

Two-parameter Weibull survival with supplied shape/scale; no fitting.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Weibull life and reliability. Inputs: shape/scale parameters or qualified failure data. Outputs: survival curve; quantiles; fitted uncertainty. Model scope: Explicit distribution, independence and sample assumptions. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: shape/scale parameters or qualified failure data
Outputs: survival curve, quantiles, fitted uncertainty
Modes: calculate, compare, sweep
Drawing: Distribution and reliability plot

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS