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Fall Arrest Clearance Calculator

Work out fall arrest clearance instantly with clear inputs, formula shown and shareable results.

About Fall Arrest Clearance Calculator

Required fall clearance is the sum of free fall, energy absorber deployment, harness stretch, the distance from the dorsal D-ring to the worker's feet, and a safety margin so the feet stop clear of the ground or obstruction. With a two metre lanyard and a shock absorber the total is typically well over six metres, which is why short lanyards or self-retracting devices are needed at lower heights.

Formula

Fall clearance

Clearance = lanyard length + absorber deployment + harness stretch + 1.5 m worker height + safety margin

Worked example

With the default values below, Fall Arrest Clearance Calculator returns Fall clearance required below the anchor of 6.65. Change any input above and every figure here is recalculated in your browser.

Inputs used

Lanyard lengthminimum 0.1 m
2 m
Energy absorber deploymentminimum 0 m
1.75 m
Harness stretch and D-ring slideminimum 0 m
0.4 m
Safety margin below the feetminimum 0 m
1 m

Results

Fall clearance required below the anchor
6.65 m
Free fall distance
2.00 m
Total arrest distance
4.15 m
Allowance for the worker below the D-ring
1.50 m

Step by step

  1. 1Values used
  2. 2Fall clearance
  3. 3Fall clearance required below the anchor= 6.65 m
  4. 4Free fall distance= 2.00 m
  5. 5Total arrest distance= 4.15 m
  6. 6Allowance for the worker below the D-ring= 1.50 m

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 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Preliminary estimate only. Fall protection systems must be selected and installed under a competent person's plan using the manufacturer's clearance data.

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 protection systems must be selected and installed under a competent person's plan using the manufacturer's clearance data.

Frequently Asked Questions

How is the Fall Arrest Clearance figure worked out?

Clearance = lanyard length + absorber deployment + harness stretch + 1.5 m worker height + safety margin. Required fall clearance is the sum of free fall, energy absorber deployment, harness stretch, the distance from the dorsal D-ring to the worker's feet, and a safety margin so the feet stop clear of the ground or obstruction.

What if the available clearance is less?

Use a self-retracting lifeline, which limits free fall to under half a metre, or a work positioning or restraint system that prevents a fall from starting at all.

What values do I need to enter?

This calculator takes 4 inputs: Lanyard length, Energy absorber deployment, Harness stretch and D-ring slide, Safety margin below the feet. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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