As Low As Reasonably Practicable Cost Calculator

Work out as low as reasonably practicable cost instantly with clear inputs, formula shown and shareable results.

About As Low As Reasonably Practicable Cost Calculator

Demonstrating that risk is as low as reasonably practicable requires comparing the cost of a measure with its monetised safety benefit, statistical fatalities averted times the value of a prevented fatality. A measure must be implemented unless its cost is grossly disproportionate to the benefit, with the disproportion factor rising as the residual risk gets closer to intolerable.

Formulas

Benefit

Benefit = statistical fatalities averted x value of a prevented fatality

ALARP test

Implement unless cost exceeds benefit x gross disproportion factor

Worked example

With the default values below, As Low As Reasonably Practicable Cost Calculator returns Cost to benefit ratio of 7.500. Change any input above and every figure here is recalculated in your browser.

Inputs used

Statistical fatalities avertedminimum 0: 0.01
Value of a prevented fatalityminimum 1: 2,000,000
Cost of the mitigationminimum 0: 150,000
Gross disproportion factoraccepts 1–30: 3

Results

Cost to benefit ratio: 7.500
Monetised benefit: $20,000.00
Cost above which the measure is grossly disproportionate: $60,000.00
ALARP decision: Grossly disproportionate — the measure is not required to demonstrate ALARP

Step by step

1Values used
2Benefit
3ALARP test
4Cost to benefit ratio= 7.500
5Monetised benefit= 20,000.00
6Cost above which the measure is grossly disproportionate= 60,000.00
7ALARP decision= Grossly disproportionate — the measure is not required to demonstrate ALARP

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 or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Preliminary estimate only. ALARP demonstrations must be prepared by competent safety specialists in line with regulator guidance and accepted values.

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

Preliminary estimate only. ALARP demonstrations must be prepared by competent safety specialists in line with regulator guidance and accepted values.

Frequently Asked Questions

How is the As Low As Reasonably Practicable Cost figure worked out?

Benefit = statistical fatalities averted x value of a prevented fatality. Demonstrating that risk is as low as reasonably practicable requires comparing the cost of a measure with its monetised safety benefit, statistical fatalities averted times the value of a prevented fatality.

Why is the disproportion factor greater than one?

Because the burden of proof falls on the duty holder. Equal cost and benefit is not enough to refuse a measure; the cost must be grossly disproportionate, and the factor rises with the severity of the residual risk.

What values do I need to enter?

This calculator takes 4 inputs: Statistical fatalities averted, Value of a prevented fatality, Cost of the mitigation, Gross disproportion factor. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.