How to Read a Climbing Carabiner: Strength Ratings Explained
How to Read a Climbing Carabiner
A climbing carabiner may look like a simple metal loop, but the markings on its spine contain important information.
If you are new to climbing equipment, numbers such as 20 kN, 8 kN, or 7 kN can be confusing.
These numbers are not random.
They describe the strength rating of the carabiner under specified loading conditions.
Understanding the markings is useful because carabiners are not all designed to handle the same loads.
What Does kN Mean on a Carabiner?
Climbing carabiners are commonly marked with strength values in kilonewtons (kN).
A kilonewton is a unit of force.
You may see three numbers on a climbing carabiner.
For example:
24 kN
8 kN
8 kN
The exact markings vary by product, but they generally represent different loading conditions.
Typical markings may refer to:
Major-axis loading with the gate closed
Minor-axis loading
Gate-open loading
Mammut explains that climbing carabiner ratings can indicate maximum breaking loads in different orientations, including axial, transverse, and open-gate loading.
Why Are There Three Strength Numbers?
A carabiner is strongest when the load is applied along its main axis and the gate is properly closed.
It can be significantly weaker if:
The load is applied sideways
The gate is open
The carabiner is loaded over an edge
The carabiner is positioned incorrectly
That is why a carabiner's strength cannot be represented by one number alone.
The shape of the carabiner, gate design, material, and loading direction all matter.
What Is the Strongest Part of a Carabiner?
The solid spine is generally the primary load-bearing part of a climbing carabiner.
The gate is a moving component, so the loading behavior is different when the gate is open.
This is also one reason carabiners should be positioned correctly during use.
REI's carabiner guide emphasizes shape, gate type, locking, size, weight, and strength as important factors when choosing climbing carabiners.
What Does an Open-Gate Rating Mean?
An open-gate rating describes the carabiner's strength when the gate is open.
This rating is normally lower than the major-axis closed-gate rating.
That difference matters.
An accidental gate opening can change the loading condition dramatically.
This is why climbing carabiners are designed with specific gate and locking systems.
Locking Carabiners vs. Non-Locking Carabiners
A locking carabiner adds another layer of control.
Common systems include:
Screw Lock
The user manually rotates a sleeve to secure the gate.
This design is relatively simple and can be useful in environments where automatic mechanisms may be affected by dirt or ice.
Twist Lock
The sleeve must be rotated before the gate can open.
It can automatically return to the locked position after the gate closes.
Other Auto-Locking Systems
Some systems use two or three actions to open the carabiner.
The exact mechanism depends on the manufacturer and product.
How Do You Read the Carabiner Markings?
When inspecting a climbing carabiner, look along the spine.
You may find:
Manufacturer name or logo
Model name
Strength ratings
Applicable certification marks
Product identification
Some climbing equipment also carries CE or UIAA-related markings where applicable.
The exact markings depend on the product and market.
Do not assume that a decorative or accessory carabiner has climbing certification simply because it has a similar shape.
Why Shape Matters
Carabiner shape affects how the connector behaves.
D Shape
A D-shaped design is versatile and directs much of the load toward the spine.
Asymmetric D
This shape offers a relatively large gate opening while keeping the design compact.
Oval
Oval carabiners provide a symmetrical shape and can be useful for equipment organization and pulley-related applications.
Pear / HMS
The wider upper section provides more room for rope handling and belaying applications.
Petzl lists D, pear, and oval shapes as common carabiner designs, each with different intended uses.
Does a Bigger Carabiner Mean a Stronger Carabiner?
Not necessarily.
Size is only one factor.
A larger carabiner may provide more internal space or a larger gate opening, but strength depends on:
Material
Cross-section
Geometry
Manufacturing method
Gate design
Loading direction
The product's actual specification is more useful than judging strength by appearance.
Why Manufacturing Quality Matters
A climbing carabiner is a safety-critical component.
Its performance depends not only on the material but also on the manufacturing process.
Important manufacturing stages may include:
Material selection
Forming or forging
Machining
Deburring
Gate assembly
Surface treatment
Inspection
Specialized climbing products must also meet the applicable standards and testing requirements for their intended market.
For this reason, a manufacturer should never make a climbing-safety claim based only on the shape of the product.
What About General-Purpose Carabiners?
This is where buyers often get confused.
A carabiner used to attach a water bottle to a backpack is not necessarily a climbing carabiner.
A small accessory clip can be perfectly suitable for its intended purpose while being completely inappropriate for fall protection.
That distinction should be clear on product pages and packaging.
A Simple Example
Imagine two carabiners.
Carabiner A
Lightweight
Small
Non-locking
Designed for accessory use
Carabiner B
Tested and certified for climbing
Specific kN ratings
Locking gate
Designed for load-bearing applications
They may look similar.
But they are not interchangeable.
FAQ
What does 20 kN mean on a carabiner?
It indicates a specified force rating under a particular test condition. It should not be interpreted as a universal "weight limit."
Are all aluminum carabiners for climbing?
No.
Aluminum is simply a material. The product's design, testing, intended use, and certification determine whether it is suitable for climbing.
Can I use a general carabiner for climbing?
Do not assume so. Use climbing equipment that is specifically designed, rated, and certified for climbing.