Lanyard Length And Force Calculator

Work out lanyard length and force instantly with clear inputs, formula shown and shareable results.

About Lanyard Length And Force Calculator

Energy from the fall, mass times gravity times total drop, must be absorbed over the deceleration distance, so average arrest force is that energy divided by the stopping distance. Standards cap arrest force at 6 kN because higher forces injure the spine and internal organs, which is why energy absorbing lanyards deploy over more than a metre.

Formulas

Arrest force

F = m g (free fall + deceleration) / deceleration distance

Fall factor

Force as a multiple of body weight = F / (m g)

Worked example

With the default values below, Lanyard Length And Force Calculator returns Peak arrest force of 2.746. Change any input above and every figure here is recalculated in your browser.

Inputs used

Worker mass including toolsminimum 20 kg: 100 kg
Free fall distanceminimum 0.05 m: 1.8 m
Deceleration distanceminimum 0.05 m: 1 m

Results

Peak arrest force: 2.746 kN
Force as multiple of body weight: 2.800
Energy to be absorbed: 2,746 J
Assessment against the 6 kN limit: Within the 6 kN maximum arrest force

Step by step

1Values used
2Arrest force
3Fall factor
4Peak arrest force= 2.746 kN
5Force as multiple of body weight= 2.800
6Energy to be absorbed= 2,746 J
7Assessment against the 6 kN limit= Within the 6 kN maximum arrest force

Assumptions and limits

The result is derived only from the 3 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 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Preliminary estimate only. Fall arrest system selection must follow the equipment manufacturer's data and the applicable standard, under a competent person's plan.

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

Preliminary estimate only. Fall arrest system selection must follow the equipment manufacturer's data and the applicable standard, under a competent person's plan.

Frequently Asked Questions

How is the Lanyard Length And Force figure worked out?

F = m g (free fall + deceleration) / deceleration distance. Energy from the fall, mass times gravity times total drop, must be absorbed over the deceleration distance, so average arrest force is that energy divided by the stopping distance.

Why is a fixed lanyard so dangerous?

With almost no deceleration distance the arrest force can exceed 15 kN, which is well beyond survivable spinal loading. Fixed lanyards are for restraint and positioning, not fall arrest.

What values do I need to enter?

This calculator takes 3 inputs: Worker mass including tools, Free fall distance, Deceleration distance. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.