Average and Max Kn in a Leader Fall?

I thought I remember reading somewhere that most falls don't go above 7kn. I can't find where I read that so I might be completely wrong.
Also in The Mountaineering Handbook by Craig Connally, the highest Kn a fall could be is 9kn. https://www.alpinesavvy.com/blog/climbing-gear-strength-ratings
Anyone know more about this?

• Most* falls, 7kn  seems consistent with tests I've seen. But it's not rare to go over that in many common scenarios. Falling 2ft directly onto an anchor could potentially break a 22kn sling. 

Daniel Melnyk wrote: I thought I remember reading somewhere that most falls don't go above 7kn. I can't find where I read that so I might be completely wrong.
Also in The Mountaineering Handbook by Craig Connally, the highest Kn a fall could be is 9kn. https://www.alpinesavvy.com/blog/climbing-gear-strength-ratings
Anyone know more about this?

Well, this thread should go on forever.  

For starters, your reference link is incorrect only four sentences in (if we are nitpicking).  

Metric notes:  A kilonewton (kN) is a metric unit of force,

correct.  

 equal to 100 kilograms,

incorrect.  A newton is a measure of force.  A kilogram is a measure of mass.  

 or about 225 lbs.  

Pounds is a measure of weight, more closely related to force.  To write "Kn" is incorrect.  k simply denominates 1000, N is more proper and refers to Sir Isaac Newton.   So, kN is correct.  For our purposes, we can say 1 kN is approx equal to 225 lbs.

What was your question?  Oh, right.  Let's get to it.  

First, we need to specify if we are talking about the force on the climber or the force on the top piece holding a lead fall. The force on the climber is known as the "impact force".  12kN "impact force" on the climber by the rope is the max allowable by the UIAA to receive their certification.  So, all dynamic climbing ropes with a UIAA cert meet this criteria.  It is useful to understand this test which is done with an 80 kg mass (~176lbs), a very high fall factor with static belay device.  (It is difficult to replicate this scenario in the real world.)  Most ropes are rated in the 7.8-9.5 range based on this test.  With this data, one can extrapolate and approximate the impact force on the climber from the rope manufacturer's rating.  A heavier person in the "test" would result in a higher impact force.  A lower fall factor would result in a lower impact force, etc.  Hence, it is very difficult to exceed the 9 kN impact on the climber, as you mentioned.  

On the other hand, the force on the top piece of gear that holds the lead fall is approximately 1.7 x the impact force.  So, 15 kN is possible on your top piece of gear if you come close to the UIAA test condition and have a mass of 80 kg.  But this is nearly impossible.  It would have to be an extremely high fall factor with a heavy leader, a heavy belayer and a very static belay.  

Here’s some good test info from the Petzl labs: ​Petzl Test Fall data​​​

Love those Petzl videos.  The 5kN rating on small gear was really bothering me until I saw what it takes to generate that kind of force.