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Bow Tie Barrier Count Calculator

Work out bow tie barrier count instantly with clear inputs, formula shown and shareable results.

About Bow Tie Barrier Count Calculator

A bow tie diagram places the top event at the centre, threats on the left with preventive barriers, and consequences on the right with recovery barriers. Counting them gives the barrier inventory that must be assigned owners, performance standards and verification activities, and the pathway count shows how many distinct escalation routes exist.

Formulas

Barrier count

Preventive = threats x barriers per threat; recovery = consequences x barriers per consequence

Pathways

Pathways = threats x consequences

Worked example

With the default values below, Bow Tie Barrier Count Calculator returns Total barriers in the bow tie of 18. Change any input above and every figure here is recalculated in your browser.

Inputs used

Threats identifiedminimum 1
4
Preventive barriers per threatminimum 1
3
Consequences identifiedminimum 1
3
Recovery barriers per consequenceminimum 1
2

Results

Total barriers in the bow tie
18
Preventive barriers
12
Recovery barriers
6
Distinct pathways through the diagram
12

Step by step

  1. 1Values used
  2. 2Barrier count
  3. 3Pathways
  4. 4Total barriers in the bow tie= 18
  5. 5Preventive barriers= 12
  6. 6Recovery barriers= 6
  7. 7Distinct pathways through the diagram= 12

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Preliminary estimate only. Bow tie analysis must be developed by a competent facilitator with operational input and each barrier assigned a performance standard.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Bow tie analysis must be developed by a competent facilitator with operational input and each barrier assigned a performance standard.

Frequently Asked Questions

How is the Bow Tie Barrier Count figure worked out?

Preventive = threats x barriers per threat; recovery = consequences x barriers per consequence. A bow tie diagram places the top event at the centre, threats on the left with preventive barriers, and consequences on the right with recovery barriers.

Is more barriers always better?

No. Barriers that are not independent, not verified or not maintained give false assurance. A small number of well managed critical barriers beats a long list of nominal ones.

What values do I need to enter?

This calculator takes 4 inputs: Threats identified, Preventive barriers per threat, Consequences identified, Recovery barriers per consequence. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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