Tool 3 of 4 · BC & Alberta

Required clearance calculator

A fall arrest system needs room below the anchor to stop you before you hit anything. Add up five lengths, A to E, and the total is the clearance you need. A rope grab on a lifeline adds two more: how far the grab slides before it locks, and how far the rope stretches. Use the figures on your own equipment’s labels and your site’s safety margin.

The same steps as Alpha’s Fall Protection course · BC OHS Regulation Part 11 ↗

ALanyard lengthThe full length, not the free fall

1.8 m5.9 ft

BShock absorber, fully openUse the figure on its label

1.2 m3.9 ft

CD-ring slip and harness stretch0.3 m for a standard harness, 0.75 m for a stretch-webbing harness

0.3 m1.0 ft

DD-ring height above your feetLonger for a taller worker

1.5 m4.9 ft

ESafety marginUse your site's figure. Alberta's worksheet sets 0.6 m as the minimum

0.9 m3.0 ft

+Swing dropOnly when the anchor is off to one side. Leave at 0 when it is overhead

0.0 m0.0 ft

You need5.7 m18.7 ft below the anchor

That is A + B + C + D + E. The room below the anchor, to the first thing you would hit, must be at least this.

What this covers: a fixed-length shock-absorbing lanyard, or a rope grab on a vertical lifeline, with the drop measured straight down from the anchor. Not self-retracting devices, horizontal lifelines or a line running over an edge: use the manufacturer’s clearance figures for those. Totals are rounded up to the next 0.1 m.

General guidance only. This tool supports, and does not replace, your own competent assessment, the site’s fall protection plan, the current BC OHS Regulation (Part 11) or Alberta OHS Code (Part 9), the manufacturer’s instructions and your employer’s procedures. Where they differ, follow the more protective one.

Read the full notice

These tools help you check. They do not replace the plan, the label or your supervisor. Your employer must instruct you in the system and procedures for each work area and authorize you to work at height. Follow the site’s fall protection plan and each manufacturer’s instructions. When the regulation, the manufacturer, the site or the plan differ, follow the more protective one.

Built from the BC OHS Regulation (Part 11), Alberta’s OHS Code (Part 9), the CSA Z259 equipment standards and manufacturers’ published instructions, as taught in Alpha Training Solutions’ Fall Protection course. Clearance figures depend on your equipment: use the numbers on the label and the safety margin your site sets. Not made or endorsed by any regulator or manufacturer.