Carabiner Strength Calculator
Compare static and dynamic loads against UIAA carabiner ratings. Understand kN markings and safety factors.
Quick Answer
UIAA minimum carabiner strength: 20 kN major axis closed, 7 kN minor axis, 7 kN gate open. A typical climbing fall generates 4-7 kN at the harness and 6-10 kN at the top bolt. Always load carabiners on the major axis with gate fully closed.
Force Analysis
Safety Factors
Critical safety rules
- Always load carabiners on the major axis (long way), never sideways
- Confirm the gate is fully closed and locked (for lockers)
- Avoid “triple-loading” (cross-loading + gate open) — strength drops to ~5 kN
- Retire carabiners after a significant drop or visible damage
About This Tool
The Carabiner Strength Calculator helps you understand the kN ratings stamped on your climbing gear and the actual forces generated in falls. Carabiners look interchangeable but their strength varies dramatically based on orientation: a properly loaded carabiner is 3-4x stronger than a cross-loaded one. Understanding this difference is fundamental safety knowledge for any climber.
What kN Means
kN = kilonewton, a unit of force. 1 kN = 1,000 newtons = about 225 lbf (pound-force) = the force of holding 102 kg in static suspension. Climbing carabiners are typically rated 20-28 kN on the major axis (closed gate), 7-10 kN on the minor axis (cross-loaded), and 7-10 kN on the major axis with the gate open. The major-axis-closed rating is the headline number — the others are warnings about how the carabiner can fail if loaded incorrectly.
UIAA and CE Standards
UIAA 121 (the global mountaineering standard) and CE EN 12275 (the European standard) define minimum strength requirements: 20 kN major axis closed, 7 kN minor axis, 7 kN gate open. Carabiners passing these standards are stamped “UIAA” and/or “CE” with a notification body number (e.g., CE 0123). Most modern carabiners exceed these minimums by 20-50%, but the certified numbers are the ones to plan around.
How Climbing Falls Generate Force
Climbing falls are governed by the Fall Factor (FF), the ratio of fall distance to rope length. FF 0 is a static hang (just gravity). FF 1 is a typical lead fall — the climber falls roughly the length of rope above the last bolt. FF 2 is the worst case: a fall directly onto the belay anchor with no protection. Dynamic ropes are designed to absorb energy, capping peak forces around 6-8 kN at FF 1 and 9-12 kN at FF 2 even with a heavy climber. UIAA-certified ropes can't exceed 12 kN impact force in standardized FF 1.78 test falls.
The Cross-Loading Danger
A carabiner loaded sideways (the short way) is 3-4x weaker than one loaded long-ways. A 24 kN major-axis carabiner is only 7-9 kN on the minor axis. Common ways to cross-load: a sloppy clip, a rope running across the gate, or the carabiner rotating during a fall. Always check that your carabiners are oriented properly. For master points and critical connections, use locking carabiners or carabiners with anti-cross-load shapes (Petzl Am'D, Black Diamond GridLock).
The Gate-Open Failure Mode
A carabiner with its gate held open (by debris, a glove, or rope) drops to about 7-10 kN strength even on the major axis. This is why locking carabiners (screwgate or auto-locking) are standard for belay device connections, master point anchors, and any single-point failure connection. Wire-gate carabiners are popular for ice climbing because they can't freeze open. Solid-gate carabiners are quieter but vulnerable to gate flutter on impact.
When to Retire Gear
UIAA recommends retiring carabiners after: any drop from height onto rock or hard surface, visible cracks or deformation, severe wear on the rope-bearing surface, or 10 years of use even without incidents. Lockers should be retired sooner if the gate mechanism gets stiff or if the threads bind. Don't buy used carabiners — you don't know their history. Retired carabiners can be marked with red tape and used for non-climbing purposes (keychains, gym bag clips).
Pair With Other Climbing Tools
Use with our climbing rope length calculator, our belay weight difference checker, our climbing grade converter, and our bouldering V-scale converter.