So, you have rock climbing fever and all your friends and family keep saying the same thing: “But isn’t that dangerous?”

Next time, explain you’re just a hopeless argonaut, and throw in a little physics to back you up. And it all starts with the father of it all, Sir Isaac Newton. Here’s a quick lesson.

N: A newton is a measurement of force. An apple creates about 1 newton. A human creates between 550 and 800 newtons.

kN: A kilonewton, or one thousand newtons, is a measurement of force of load. One kN is equal to about 225 pounds. Kilonewtons are used to measure things like industrial fasteners capable of withstanding massive forces, earth anchors for skyscrapers and even rocket engines.

They are also a standard rating for rock climbing equipment.

The simple act of climbing applies minimal load on climbing gear and fixed equipment for the climbing route. While the safety measurements are always in place, there are not always loaded, or strained.

When a climber falls, especially lead climbing (see how to: quickdraws), they are capable of creating tremendous force. If a 175-pound climber fell 6 feet with 6 feet of rope that stretches almost another 2 feet, they would create a force of about 5 kN, or 1,125 pounds.

The rope, being dynamic and stretching, increases the time it takes the falling climber to stop, reduces the overload in the system. In short, the longer it takes the climber to stop falling, the less the force of the load.

This system is strong.

Just how strong is the gear that people trust with their lives? Here is a list of some of the most important pieces of the puzzle:

Belay Loop

15 kN, 3,375 pounds

Belay on a climbers harness loops must be tested for 3 full minutes under load.

Locker biner

24 kN, 5,400 pounds


12kN, 2700 pounds

Ropes are dynamic – stretching up to 30 percent. The design is called kernmantle, a strong inner core with a protective outer sheath.


62 kN, 13,450 pounds

Quickdraws are composed of three parts: two carabiners, about 20 kN each, and one draw, or pre-sewn webbing length, about 22 kN.


25 kN, 5,625 pounds

Bolts are typically concrete anchors from the construction industry, drilled and hammered in or glued with epoxy.

Figure 8 knot

This sailing stopper knot, when tied properly, does not come untied. In fact, the more force applied to the knot, the tighter it gets.