It’s natural to think that a carabiner designed for belaying, with a large diameter and generally burly appearance, would be stronger than what are sometimes called a “paperclip” carabiner, used by many climbers merely for racking gear.
Let's have a look at the Petzl Attache, a long time at workhorse belay carabiner that's been around forever, and the Camp Nano, which I believe is currently the lightest carabiner on the market.
No contest, right? The yellow carabiner has to be stronger. Just look at that thing, it’s stout!
But . . . let’s check the numbers.
Stamped on the side of every climbing rated carabiner are three important load ratings: end to end, cross load, and open gate. Readings are given in kilonewtons (kN), which is a metric unit of force, equal to about 100 kg, or 220 pounds.
End to end: 23 kN
Cross load: 7 kN
Open Gate: 6 kN
End to end: 21 kN
Cross load: 8 kN
Open Gate: 9 kN
Surprised? Yeah, me too!
The Petzl Attache is stronger in the normal configuration, but the tiny Camp Nano is stronger in the cross loaded and open gate rating.
And check out the weight difference. The Petzl Attache at 78 grams weighs more than 3 TIMES the Camp Nano at 23 grams!
So, at 1/3 the weight, the Nano is stronger in two of the three carabiner strength ratings.
(This is more a tribute to modern engineering practices then any practical application, because any quality modern carabiner is strong enough for just about any use you can put to it, more below.)
Sometimes, you may hear people say, “I want to use that big, heavy, sturdy-looking carabiner because it’s stronger!” You might remind them of this post, or to have a look at the actual rating on the carabiner. The smallest carabiner on your rack may turn out to be “stronger” than the biggest one.
So, the Good News: pretty much all legit climbing carabiners you can buy have a CE rating. (“CE” is a certification mark that indicates conformity with health, safety, and environmental protection standards for products sold within the European Union.) CE ratings can vary a tiny bit depending on whether they are belay, oval, wiregate, but the general specs are: a MINIMUM strength of 20 kN end to end, 7 kN cross load, and 7kN open gate.
So, every CE rated carabiner is strong enough for any application you could ever think of. So relax, buy quality carabiners, and don’t worry about how strong they are.
(Just avoid open gate and cross loading on ANY carabiner.)
And if you want a deep dive into all things carabiner, this Black Diamond webpage is terrific.