Work out lanyard length and force instantly with clear inputs, formula shown and shareable results.
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.
Arrest force
F = m g (free fall + deceleration) / deceleration distance
Fall factor
Force as a multiple of body weight = F / (m g)
Preliminary estimate only. Fall arrest system selection must follow the equipment manufacturer's data and the applicable standard, under a competent person's plan.
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.
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.
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.