TL;DR: Carabiner weight capacity runs from under 100 lbs (unrated keychain stuff) to over 10,000 lbs (steel rigging). Climbing carabiners are rated in kilonewtons (kN) for major-axis breaking strength, typically 20–30 kN (4,500–6,750 lbs). Industrial carabiners use Working Load Limit (WLL), which is exactly 1/5 the breaking strength.
Reading a Carabiner Rating: The Three Numbers That Actually Matter
Life-safety carabiners have three numbers stamped on the spine. CE EN 12275 requires manufacturers to display these ratings in kilonewtons alongside standardized pictograms.
They represent the Minimum Breaking Strength (MBS) in three loading scenarios.
| Rating Symbol | Meaning | Typical Value (Climbing) |
|---|---|---|
| ↕ (Up/Down Arrows) | Major Axis: Strength when pulled end-to-end along the spine. | 20 kN to 30 kN |
| ↔ (Left/Right Arrows) | Minor Axis: Strength when cross-loaded across the gate and spine. | 7 kN to 9 kN |
| ⟷ (Open Gate Icon) | Gate Open: Strength when the gate is unlatched or broken. | 7 kN to 9 kN |
A carabiner hits its rated strength only when fully closed and loaded along the major axis. Deviate from that and the breaking strength drops 60% to 70%.
kN, MBS, and WLL — Why the Same Carabiner Has Three “Weight Limits”
One kilonewton equals roughly 224.8 pounds of force. Climbing manufacturers rate gear using Minimum Breaking Strength (MBS). If a carabiner is stamped 24 kN, the manufacturer guarantees it will not break until it sees at least 5,395 pounds of force.
Industrial rigging, theatrical rigging, and overhead lifting don’t operate on MBS for daily work. They use a Working Load Limit, which applies a safety factor to the MBS to account for material fatigue, dynamic shock, and the fact that people do dumb things with gear.
The standard rigging safety factor is 5:1. Overhead lifting often requires 10:1.
That creates a huge gap between recreational and industrial numbers. A Black Diamond RockLock has an MBS of 24 kN (5,395 lbs). Under a 5:1 industrial safety factor its effective WLL is 1,079 lbs. Under a 10:1 overhead lifting factor it drops to 539 lbs. Same piece of metal, three legitimate “limits,” depending on who’s asking.
The Master Capacity Chart — All Carabiner Types Compared
Carabiner major-axis strength spans from unrated keychain clips to 70+ kN steel rigging hardware.
| Carabiner Type | Example Model | Major Axis MBS | Minor Axis MBS | Gate Open MBS | WLL (5:1 Factor) | Primary Use |
|---|---|---|---|---|---|---|
| Climbing D-Shape | Petzl Sm’D | 23 kN (5,170 lbs) | 8 kN (1,798 lbs) | 7 kN (1,573 lbs) | N/A (Climbing) | Sport/Trad Climbing |
| Climbing HMS/Pear | BD RockLock | 24 kN (5,395 lbs) | 8 kN (1,798 lbs) | 8 kN (1,798 lbs) | N/A (Climbing) | Belaying / Rappelling |
| Aluminum Rigging | Petzl Am’D | 27 kN (6,069 lbs) | 8 kN (1,798 lbs) | 7 kN (1,573 lbs) | 1,213 lbs | Rescue / Light Rigging |
| Steel Rigging | DMM Klettersteig | 50 kN (11,240 lbs) | 14 kN (3,147 lbs) | 14 kN (3,147 lbs) | 2,248 lbs | Industrial / Theatrical |
| Utility Accessory | Nite Ize S-Biner #5 | Unrated | Unrated | Unrated | 100 lbs (Max) | Keys / Water Bottles |
Note: Climbing carabiners don’t carry an official WLL because recreational climbing relies on dynamic ropes to absorb force instead of static safety factors.
The variance within categories mostly comes down to material and shape. D-shaped biners push the load toward the solid spine, which is where the strength lives. HMS (pear-shaped) carabiners center the load on the wider basket for rope clearance, and that geometry costs you a bit of breaking strength.
Climbing Carabiners — What the Numbers Really Mean on the Wall
This is where most people get the math wrong, so I want to spend some time here.
The UIAA 121 standard requires climbing carabiners to hold at least 20 kN (4,496 lbs) on the major axis. That number dwarfs any human bodyweight, which is why beginners always ask why we need “4,500 pounds” of hardware for a 160-pound climber. The answer is that you aren’t the load. The fall is.
When a lead climber falls, the rope catches them and dumps all that kinetic energy into the top piece of gear. A severe lead fall generates roughly 5 kN to 7 kN of peak force on that top piece. So a 20 kN carabiner gives you about a 3:1 margin against the absolute worst case. That’s not a comfortable margin, that’s a working margin. You eat into it fast once anything else goes wrong.
And something else usually does go wrong. The real killer isn’t a major-axis break, it’s a gate-open failure. Gate flutter during a fall, the gate hooked over an edge, rope whipping across the nose at the wrong instant — any of these drop the carabiner from its stamped 24 kN down to maybe 7 kN. That’s 1,573 lbs. A hard lead fall can generate 1,500 lbs on the top piece. You can do the arithmetic.
This is why experienced climbers obsess about carabiner orientation on bolts and gear, and why the keylock nose became standard a decade ago. Cross-loading a biner on a quickdraw dogbone is the same category of problem. Obviously you wouldn’t rig a quickdraw with the rope-end biner on the bolt, but I’ve watched gym climbers do exactly that.
Gate strength is a bigger deal than most climbers appreciate. Think about that when you’re clipping.
Industrial, Rigging, and Rescue Carabiners — Where WLL Rules
Workplace and rescue carabiners follow regulatory standards that explicitly reject recreational climbing gear.
NFPA 2500 (which recently absorbed NFPA 1983) governs fire and rescue equipment. It splits carabiners into two buckets:
- Technical Use (T-Rated): 27 kN (6,069 lbs) minimum. Single-person loads.
- General Use (G-Rated): 40 kN (8,992 lbs) minimum, for two-person rescue loads.
For construction and fall arrest, OSHA and ANSI run the show. ANSI Z359.12 requires fall arrest connectors to hold 5,000 lbs (22.2 kN) on the major axis. The bigger deal: Z359 also requires the gate itself to withstand 3,600 lbs (16 kN) of direct force in any direction. Standard climbing carabiners fail that gate test immediately. This is the single most common thing people get wrong when they bring their climbing rack onto a jobsite.
Industrial rigging carabiners are almost exclusively steel. Steel gives you higher MBS (often 45 kN to 70 kN) and holds up to the abrasive wear of steel cables and rigging plates in a way aluminum just doesn’t.
Utility, Accessory, and Keychain Carabiners — “Not for Climbing” Explained
Hardware store carabiners and keychain clips carry no CE or UIAA certification. Manufacturers stamp “NOT FOR CLIMBING” on the spine as liability cover.
These clips don’t get batch-tested for MBS. Brands that bother to publish any number test for static utility loads only. The Nite Ize S-Biner Size #4 holds 75 lbs; the Size #5 holds 100 lbs.
Utility carabiners fail instantly under dynamic shock. A 200-pound person sitting down hard in a hammock can generate somewhere in the ballpark of 400 to 600 pounds of instantaneous force. Keychain biner snaps, person hits the deck. Hammock suspensions want a wiregate climbing carabiner rated to at least 12 kN.
What Degrades a Carabiner’s Rated Capacity
The persistent myth: dropping a carabiner on concrete creates invisible “microfractures” that quietly destroy its strength. Independent testing and manufacturer statements both say no. Petzl and Black Diamond are on the record that a dropped carabiner remains safe unless you can see deformation, sharp burrs, or a gate that isn’t behaving.
Metal carabiners have an indefinite shelf life. Age and UV don’t degrade aluminum or steel. Physical wear is a different story, and that’s what actually puts biners in the retirement bin.
Petzl’s retirement guidelines say destroy it if:
- The rope groove wears deeper than 1 mm.
- The gate doesn’t close and lock on its own.
- The rivet is bending or loose.
- You see chemical corrosion. (Common in saltwater work.)
Heat exposure is the sneaky one. A biner in a hot car trunk is fine. A biner that got close to a structural fire or a careless shop torch has lost its heat treatment and needs to go in the trash, even if it looks perfect. You cannot see temper loss.
I still retire aluminum biners earlier than the official guidelines call for, honestly. Old habit from rescue work, not something I can defend on the data.
Choosing the Right Carabiner for Your Actual Load
Pick based on load type and the regulatory environment, in that order.
Hanging a 200 lb hammock: Static hang with some bouncing. Any standard 12–20 kN aluminum wiregate climbing carabiner gives you massive margin. Don’t use hardware store clips.
Top-roping: Life-safety recreational load. UIAA or CE certified locking carabiner, 20 kN minimum major axis.
Rigging a 500 lb theatrical light: Static industrial load suspended over people’s heads. 10:1 safety factor applies. MBS needs to be at least 5,000 lbs (22.2 kN). A steel locker rated 30+ kN clears this without thinking.
Fall arrest for a 250 lb worker: Regulated workplace life-safety. ANSI Z359.12 auto-locking carabiner, 5,000 lb major axis, 3,600 lb gate. Climbing carabiners are not legal for this.
FAQ
How many pounds is 25 kN on a carabiner?
About 5,620 lbs. One kN is 224.8 pounds. Breaking strength, not safe working load.
Can I use a climbing carabiner for rigging or lifting?
No. Climbing carabiners don’t meet the 3,600 lb gate strength ANSI requires for workplace fall arrest, and they don’t carry a certified Working Load Limit. For overhead lifting, OSHA wants a WLL, and a climbing biner can’t give you one. There’s also the inspection paper trail problem — rigging gear has to be traceable in a way recreational gear isn’t, and your safety officer will reject a RockLock on sight even if the math technically works. Use the right tool.
What’s the weight limit on a keychain carabiner?
10 to 100 lbs static, depending on size. Unrated for dynamic shock. Snaps instantly under hammock use, large-dog tie-outs, or human weight.
What does “MBS” mean on a carabiner?
Minimum Breaking Strength. The force at which the carabiner physically fails in a lab test. Not a daily use limit.
How often should I replace my carabiner?
When it wears out, not on a schedule.
