If you’re new to climbing, you might look at some of the carabiners on the market and wonder how something so small and light could possibly be trusted with your life. Yet every year, gear gets lighter—and stronger.
Any carabiner made for climbing will have a series of numbers and markings on the spine (the side opposite the gate). Look closely and you’ll find three sets of numbers followed by “kN,” each representing a different strength rating. One set has vertical arrows, another horizontal arrows, and the last shows a tiny image of a carabiner with the gate open.
Do the Math
“kN” stands for kilonewton—a unit of force. One kilonewton equals roughly 225 pounds of force. The first number (usually the highest) is the major axis rating—how much force the carabiner can withstand when loaded end-to-end with the gate closed. For example, a 24 kN rating means it can hold about 5,400 lbs of force.
The second number, marked with horizontal arrows, shows the minor axis strength—how much the carabiner can take if it’s crossloaded (force applied sideways across the gate and spine). This number is usually much lower. A 7 kN minor axis rating means the carabiner can hold around 1,575 lbs in that orientation.
The third number, often close to the minor axis rating, is the open gate strength. As the name suggests, it shows how strong the carabiner is with the gate open. If it reads 8 kN, that’s about 1,800 lbs of force.
Force vs. Weight
There’s a difference between static weight and dynamic force. Climbing gear is rated for force, not just dead weight. A fall generates much more force than simply hanging. That’s why climbing-rated carabiners shouldn’t be used for other purposes like winching or industrial rigging—those jobs require steel carabiners built for different standards. And if you do use your aluminum gear for something outside of climbing, it’s best to retire it afterward.
Certifications Matter
Most climbing carabiners also carry a CE and/or UIAA certification, stamped near the strength ratings. While not legally required in the U.S., these marks show the gear has passed international standards for safety and performance. Avoid carabiners without at least one of these—it’s not worth saving a few bucks on life-support gear.
Final Thoughts
Climbing carabiners are strongest when loaded on the major axis with the gate fully closed. While the minor and open gate ratings may still sound strong, the forces generated in a fall—especially a short one with little rope to absorb impact—can quickly exceed them.
If you want hands-on experience with this kind of technical knowledge, many of these principles are covered in my AntiGravity Training workshops, out in the field where they matter most. Check out the Workshops page to learn more and find an upcoming class that fits your goals.
