Friday, July 31, 2015

Understanding Fall Factors

Many climbers don't really understand fall factors. But it's actually is quite straightforward. Fall factors may be determined by a simple formula:

Fall Factor = Length of Fall/Length of Rope

Using this formula, you can determine how hard you've hit the anchor. A factor 2 is the maximum that may be attained in a typical climbing fall, since the height of a fall can't exceed two times the length of the rope. Under normal circumstances, a factor 2 fall can only occur when a leader has no protection and he falls past the belayer. Once protection is placed, the distance of the fall as a function of the rope length is lessened, and the Fall Factor drops below 2.

A fall of 30 feet is significantly more serious if it takes place with 15 feet of rope out after the climber has placed no protection and falls past the belayer, than if it occurs 100 feet above the belayer (a fall factor of 1.15), in which case the dynamic stretch of the rope more effectively cushions the fall.

A factor 2 fall is very bad. Indeed, it is actually possible that an anchor may fail in the event of such a fall. As such, it is imperative that climbers place gear immediately after they start to climb as they leave a belay station. This will limit the possibility of a bad fall.

In the following video a climber is approximately twenty-five feet out from his belayer. He falls eight feet above his last piece of pro. With rope stretch and slippage he actually falls approximately twenty feet. That piece of pro eight feet below makes his rather large fall totally acceptable with a fall factor of 1.32.

If you are interested in finding out what kind of fall factors you've sustained or might have come close to sustaining, an online fall factor calculator may be found here.

After a breakdown of fall factors such as this, some people will still be confused. So the question must be asked, what are the main points that you should take away from this? They're actually quite simple:
  1. Always put in a piece immediately after you climb away from the anchor. This will protect your anchor from sustaining a factor 2 fall.
  2. This should be an obvious one. Always use a dynamic rope that is in good shape.

--Jason D. Martin


There are two problems with this post that were pointed out in the comments below.  First, my math is a bit off in the last paragraph above the video.  And second, the online fall factor calculator doesn't appear to be working properlyNot surprisingly, I used the faulty calculator to come up with my number.  The actual fall factor would be 0.8.

Special thanks to the two anonymous commentators who pointed these things out.



Anonymous said...

Nice post, very informative as usual.
However, the calculator linked is terrible. Try these inputs:
150lb weight
100 ft rope out
1 ft from last anchor

Since when is that a fall factor 1.01?
Isn't it more like:
1 ft from anchor = 2 ft fall
2/100 = Fall factor of 0.2

Anonymous said...

Howdy, Good discussion here.
But can I get some math verification real quick. If the guy in the video falls 8ft above his piece, that is 16ft before stretch, and you say about 20ft total. He is about 25ft from his belayer. So 20ft fall/25ft rope out = 0.8Fall Factor. He would have to fall 33ft with 25ft of rope out to get a 1.32 Fall Factor. Can I get a clarification of this?

American Alpine Institute said...

Anonymous Posters,

Thanks for your comments. Please see amendment to my blog above.


Anonymous said...

Just climb people!!

Enjoying the view, day, -or-fall is not about calculations, it's just about living in that moment, & learning from it!!

Please don't fall back on your gear when you should be relying on yourself to get up the rock!!!!!!!!!!!!!!!!!!!!!!!!

American Alpine Institute said...

American Alpine Institute said...


We appreciate your zeal for the mountains, however this blog is supposed to educate people who have questions about common discussions in climbing; in this case fall factors.

For us to focus solely on climbing, it is important to have understanding of the equipment we use and its limitations to maintain safety.

-Andrew Yasso, Program Coordinator