To calculate the required safety harness fall clearance, you must sum the distances for Free Fall, Deceleration Distance, Harness Stretch/Worker Height, and a Safety Factor. The Free Fall Distance is the distance the worker falls before the fall arrest system activates. The Deceleration Distance is how far the fall arrest device slows the fall. Harness stretch and the worker's height are combined to determine the total distance the D-ring moves upward. Finally, a Safety Factor is added as a buffer to prevent contact with the surface below. 
Components of Fall Clearance

• Free Fall Distance:
  The distance the worker falls before the fall arrest system activates. For a lanyard, this can be the lanyard length, but for a self-retracting lifeline (SRL), it is typically limited to 2 feet (0.6m). 
• Deceleration Distance:
  The distance the energy absorber or shock-absorbing lanyard takes to slow the fall. 
• Harness Stretch and Worker Height:
  This accounts for how the worker's body stretches and how high the D-ring attachment point moves during a fall. It is often simplified by using the average worker's height. 
• Safety Factor:
  A mandatory additional buffer distance to ensure the worker does not strike the surface below. This buffer helps account for variations in worker weight, miscalculations, and other unforeseen issues. 

Steps for Calculation

1. 1. Determine Free Fall Distance:
   Measure the maximum potential free fall, which varies based on the type of fall protection used. 
2. 2. Find Deceleration Distance:
   Consult the fall arrest device's manufacturer for the specific deceleration distance. 
3. 3. Account for Harness Stretch and Worker Height:
   Estimate the distance the D-ring will move by considering the worker's height and the potential for the harness to stretch during a fall. 
4. 4. Add a Safety Factor:
   Include a minimum safety factor, such as 2 feet (0.6m), to create a necessary buffer. 
5. 5. Sum the Values:
   Add all these distances together to get the total required fall clearance. 

Example Calculation
Using a standard lanyard, the total fall clearance calculation might look like this: 

• Free Fall Distance: 6 feet (lanyard length)
• Deceleration Distance: 3.5 feet
• Worker/Harness Stretch: 6 feet (average worker height)
• Safety Factor: 2 feet
• Total Fall Clearance: 6 + 3.5 + 6 + 2 = 17.5 feet