What is fall clearance distance?

Fall clearance distance is the minimum vertical distance below a worker's anchor point (or the working level) that must be free of obstructions so the fall arrest system stops the worker before they hit a lower level. It is the free-fall distance (lanyard length or SRL activation), plus the deceleration distance, plus the distance from the D-ring to the worker's feet when suspended, plus a safety margin.

What is the difference between a shock-absorbing lanyard and a self-retracting lifeline?

A shock-absorbing lanyard is a fixed-length connector (typically 1.8 m) with a built-in energy absorber that deploys during a fall to reduce peak arrest force. It allows a larger free fall and needs more clearance below. A self-retracting lifeline (SRL) pays out and retracts like a seatbelt and locks within a short distance, so the free fall and total clearance are much smaller. SRLs are preferred where clearance is limited. Always use the figures on the equipment label.

What is deceleration distance?

Deceleration distance is the distance travelled after the system starts to engage until the worker stops. OSHA 29 CFR 1926.502(d)(16) limits it to 3.5 ft (1.07 m) for a personal fall arrest system, and this calculator defaults to 1.07 m for lanyards. For SRLs the braking distance is much shorter, and this calculator defaults to 0.6 m. Use the manufacturer's rated value where it is available.

Why does worker height matter in fall clearance?

After a fall is arrested the worker hangs from the D-ring (between the shoulder blades), so their feet hang well below it. If this is ignored, the feet can still strike the lower level. A typical figure is about 1.5 m from D-ring to feet. If you enter the worker's height instead, this calculator estimates it as 0.85 times the height (1.49 m for a 1.75 m worker). It is an approximation, so prefer the manufacturer's data or a measured value.

What is swing fall and why does this formula not always apply?

Swing fall (pendulum effect) occurs when the anchor point is not directly above the worker at the moment of a fall. The worker swings like a pendulum and can strike a wall, column or other obstruction. The clearance formula covers only vertical clearance for a straight-down fall. In a swing-fall scenario lateral clearance must also be assessed.

When does the standard fall clearance formula not apply?

The standard formula does not apply when the worker is connected to a horizontal lifeline (which deflects in a fall), when the anchor point is below the worker's feet or shoulder height, when a work-positioning system is used instead of fall arrest, when the surface below is sloped, or when multiple anchor transitions are involved. In these cases manufacturer-specific calculations or a competent person must assess the system.

Fall Clearance Calculator — Lanyard & SRL (AS/NZS 1891)

Calculate fall clearance distance for shock-absorbing lanyards and self-retracting lifelines. FFD, deceleration, body suspension and safety factor. PASS/FAIL.

Last updated: 6 October 2026

Disclaimer: This calculation is a planning estimate only. Actual fall-arrest system selection and anchor point assessment must be performed by a competent person. Always follow the manufacturer's system label and relevant standards (AS/NZS 1891, ANSI/ASSP Z359).

Connector type

Units

Lanyard length (m)

Anchor offset (m)

Positive if the anchor is above the D-ring (takes up slack, less free fall), negative if below it (adds free fall). 0 = anchor at D-ring height.

Deceleration distance (m)

Safety factor margin (m) — min 0.6 m

Height below D-ring when suspended

Derive from worker height (uses 85% of height)

Enter HBS directly (m) — height from D-ring to feet when suspended

Available clearance below working level (m) (optional — for PASS/FAIL)

Clearance components

Free-fall distance (FFD)1.80 m

Deceleration distance (DD)1.07 m

Height below D-ring when suspended (HBS)1.50 m

Safety factor margin (SF)0.90 m

Total Required Clearance5.27 m

FFD = free-fall distance, DD = deceleration distance, HBS = height below d-ring when suspended, SF = safety factor margin

Fall clearance stack
Component	Distance (m)
Free-fall distance	1.80
Deceleration distance	1.07
Height below D-ring when suspended	1.50
Safety factor margin	0.90
Total required clearance	5.27

Required clearance: 5.27 m

Enter available clearance to see PASS/FAIL verdict.

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Falls from Height: A Leading Cause of Workplace Fatality

Falls from height remain one of the largest causes of workplace fatalities in Australia. In 2024, Safe Work Australia recorded 24 worker deaths from falls from a height, 13% of the 188 worker fatalities that year, second only to vehicle incidents. The vast majority of these are preventable with proper hazard assessment, correct system selection, and adequate clearance verification — which is what this calculator addresses.

When a fall arrest system stops a falling worker, it must do so before the worker contacts a lower level or obstruction. This requires that the total required clearance distance — the sum of four components — is less than the actual available clearance at the work location.

The Fall Clearance Formula

Required Clearance = FFD + DD + HBS + SF

Where:
  FFD = Free-Fall Distance  (lanyard length minus any anchor height above the D-ring, never below 0;
                               SRL activation distance plus any distance the anchor is below the D-ring)
  DD  = Deceleration Distance  (up to 1.07 m / 3.5 ft for lanyards; ~0.6 m for SRLs)
  HBS = D-ring to feet when suspended  (~1.5 m, or worker_height × 0.85)
  SF  = Safety Factor Margin  (default 0.9 m / 3.0 ft; this tool's minimum is 0.6 m)

Example (shock-absorbing lanyard, 1.75 m worker):
  FFD = 1.8 m (lanyard)
  DD  = 1.07 m
  HBS = 1.75 × 0.85 = 1.49 m
  SF  = 0.9 m
  Required = 1.8 + 1.07 + 1.49 + 0.9 = 5.26 m

Fall Arrest vs Restraint — Understanding the Difference

Fall arrest systems (lanyards, SRLs, inertia reels) are designed to stop a worker who has already fallen. They require adequate clearance below the work position. Fall restraint systems prevent a worker from reaching an unprotected edge entirely — they do not require the same clearance calculations but require careful rope/lanyard length management to prevent reaching the edge. Both systems require appropriate anchor points that are rated for the load. In the US, OSHA 29 CFR 1926.502(d)(15) requires 5,000 lb (22.2 kN) per attached worker, or a design by a qualified person with a safety factor of at least two. Australian and New Zealand anchorage requirements come from the AS/NZS 1891 series and the equipment manufacturer, so have a competent person confirm them.

Lanyard vs SRL — When to Use Each

Shock-absorbing lanyard: Best for work on fixed structures where clearance is confirmed to be adequate. Simple, low-maintenance, no moving parts. Needs roughly 5 m or more in total with the defaults above.
Self-retracting lifeline (SRL): Best where clearance is limited (e.g., work above a mezzanine floor, on scaffolding, or near lower levels). SRLs arrest falls much faster and need roughly 3.5 m with the defaults above. More expensive but dramatically reduces fall distance.

Swing Fall Hazard

One of the most underestimated hazards in fall protection is the swing fall (pendulum effect). If a worker falls while not directly below the anchor point, they will swing in an arc — potentially striking walls, columns, equipment, or edge protrusions at high speed. General guidance: keep the anchor within 15° of directly above the work position. For horizontal lifeline systems, the D-factor (deflection factor) significantly increases the effective free-fall distance and must be calculated separately using the manufacturer's documentation.

Australian and International Standards

In Australia, the selection and use of fall protection equipment is governed by: AS/NZS 1891 series (Industrial Fall-Arrest Equipment — Harnesses, Lanyards, Connectors, Inertia Reels); AS/NZS 4488 series (Industrial Rope Access); and the model WHS Regulations under the WHS Act 2011. In the US, ANSI/ASSP Z359 series covers fall protection equipment and fall protection program requirements. Both frameworks mandate competent person assessment of anchor points and system selection.

Frequently asked questions

What is fall clearance distance?: Fall clearance distance is the minimum vertical distance below a worker's anchor point (or the working level) that must be free of obstructions so the fall arrest system stops the worker before they hit a lower level. It is the free-fall distance (lanyard length or SRL activation), plus the deceleration distance, plus the distance from the D-ring to the worker's feet when suspended, plus a safety margin.
What is the difference between a shock-absorbing lanyard and a self-retracting lifeline?: A shock-absorbing lanyard is a fixed-length connector (typically 1.8 m) with a built-in energy absorber that deploys during a fall to reduce peak arrest force. It allows a larger free fall and needs more clearance below. A self-retracting lifeline (SRL) pays out and retracts like a seatbelt and locks within a short distance, so the free fall and total clearance are much smaller. SRLs are preferred where clearance is limited. Always use the figures on the equipment label.
What is deceleration distance?: Deceleration distance is the distance travelled after the system starts to engage until the worker stops. OSHA 29 CFR 1926.502(d)(16) limits it to 3.5 ft (1.07 m) for a personal fall arrest system, and this calculator defaults to 1.07 m for lanyards. For SRLs the braking distance is much shorter, and this calculator defaults to 0.6 m. Use the manufacturer's rated value where it is available.
Why does worker height matter in fall clearance?: After a fall is arrested the worker hangs from the D-ring (between the shoulder blades), so their feet hang well below it. If this is ignored, the feet can still strike the lower level. A typical figure is about 1.5 m from D-ring to feet. If you enter the worker's height instead, this calculator estimates it as 0.85 times the height (1.49 m for a 1.75 m worker). It is an approximation, so prefer the manufacturer's data or a measured value.
What is swing fall and why does this formula not always apply?: Swing fall (pendulum effect) occurs when the anchor point is not directly above the worker at the moment of a fall. The worker swings like a pendulum and can strike a wall, column or other obstruction. The clearance formula covers only vertical clearance for a straight-down fall. In a swing-fall scenario lateral clearance must also be assessed.
When does the standard fall clearance formula not apply?: The standard formula does not apply when the worker is connected to a horizontal lifeline (which deflects in a fall), when the anchor point is below the worker's feet or shoulder height, when a work-positioning system is used instead of fall arrest, when the surface below is sloped, or when multiple anchor transitions are involved. In these cases manufacturer-specific calculations or a competent person must assess the system.