Free height at fall protection
Is there room enough under you for the damper to work?
The free height is a sum of five terms — not just the rope length. Enter the figures from your own equipment's marking, and see how much clearance there must be under the anchor point before the equipment can stop you without you hitting anything.
Result
There must be at least
5.65 m
clear under the anchor point — otherwise you hit something before the equipment has stopped you.
That's how it distributes
- Free fall before the lanyard tightens1.00 m
- Fall damper extension1.75 m
- Harness extent0.40 m
- Fra D-ring til fødder1.50 m
- Safety distance to the substrate1.00 m
Fall factor
0.50
The anchor point sits around harness height.
The fall factor is the free fall divided by the rope length. If the anchor point is overhead, it is almost 0. If it is at your feet, it is 2 — and then you fall twice the rope length before the rope even tightens.
What the calculation does not know
Whether the anchor point can support a fall, whether there is something to hit on the way down, and whether you can be lowered down again afterwards — this can only be decided on site. A rescue plan is part of the setup, not something you make when someone is hanging in the harness.
In depth: the calculation with your numbers
The calculation with your numbers
- Free fall before the lanyard tightens: max(0; 2 − 1) + 0 = 1 m
- There must be at least: 1 + 1.75 + 0.4 + 1.5 + 1 = 5.65 m
- Fall factor: 1 / 2 = 0.5
What if a number is 10 % larger or smaller?
The answer when one field is changed at a time. Then you can see which number matters most — and where you need to measure precisely.
There must be at least: 5.65 m with your numbers
| Field | −10 % | +10 % |
|---|---|---|
| The anchor point above the harness's D-ring | 5.75 m (+1.8 %) | 5.55 m (−1.8 %) |
| The rope's length with carabiners | 5.45 m (−3.5 %) | 5.85 m (+3.5 %) |
| Fall damper extension | 5.48 m (−3.1 %) | 5.83 m (+3.1 %) |
| Harness extent | 5.61 m (−0.7 %) | 5.69 m (+0.7 %) |
| From D-ring to your feet | 5.5 m (−2.7 %) | 5.8 m (+2.7 %) |
| Safety distance to the substrate | 5.55 m (−1.8 %) | 5.75 m (+1.8 %) |
Matters most for the answer: The rope's length with carabiners
What if the anchor point is moved?
Same equipment and same body — only the anchor point's position changed:
| Anchor point | Fall factor | Free fall before the lanyard tightens | There must be at least |
|---|---|---|---|
| Lanyard length above the D-ring (2 m) | 0 | 0 m | 4.65 m |
| Level with the D-ring (0 m) | 1 | 2 m | 6.65 m |
| Lanyard length below the D-ring (-2 m) | 2 | 4 m | 8.65 m |
| Your anchor point (1 m) | 0.5 | 1 m | 5.65 m |
Formula
H = h_frit + h_dæmper + h_sele + h_krop + h_margin
fall factor = h_frit / L_line
Indicative
The result is indicative and an aid tool for estimates and learning. It does not replace design, applicable standards and legislation or a qualified professional's specific assessment. Always check against the source (EN 363 · fall protection system) and actual conditions on the task. See sources & reservations.