In the lifting, rigging, and manufacturing industries, accurately understanding force and capacity specifications is critical to safety. This guide breaks down the International System of Units (SI) for force and explains the essential terminology used to rate lifting equipment.
The SI derived unit of force, named after Isaac Newton. One newton is the force required to accelerate a mass of 1 kg at a rate of 1 meter per second squared.
Commonly used in European specifications for lashings and tie-downs.
1 daN = 10 N
Used for stating safety holding values of heavy equipment, anchors, and climbing gear (karabiners).
1 kN = 100 daN = 1000 N
On Earth's surface, a mass of 1 kg exerts a force of approximately 9.8 N downwards.
1 kgf = 9.80665 N
An amusing and easy way to help remember the newton (N): On earth, 1 N is equivalent to approximately 100 grams (g). Coincidentally, this is about the mass of a standard apple. So, you can think of 1 N as the force of getting hit on the head with an apple. Similarly, 1 kN equals roughly 100 kg of load (technically 101.97 kg, but using 100 is a safer, easier engineering estimate).
| Stated Specification | In Kilonewtons (kN) | In Dekanewtons (daN) | Approximate Weight (kg) |
|---|---|---|---|
| Strength: 18 kN | 18 kN | 1800 daN | ~ 1800 kg |
| Breaking strain: 2000 daN | 20 kN | 2000 daN | ~ 2000 kg |
| Breaking load: 2500 kg | 25 kN | 2500 daN | ~ 2500 kg |
| Guaranteed load: 26 kN | 26 kN | 2600 daN | ~ 2600 kg |
| Breaking load: 32 kN | 32 kN | 3200 daN | ~ 3200 kg |
| Breaking strength: 40 kN | 40 kN | 4000 daN | ~ 4000 kg |
Also known as Safe Working Load (SWL), this is the maximum working load designed by the manufacturer. It is the exact force that a piece of lifting equipment, device, or accessory can safely use to lift, suspend, or lower a mass without fear of yielding or breaking.
Also known as Minimum Breaking Strength (MBS). The WLL represents a force that is much less than what is required to make the lifting equipment fail. The absolute point of failure or rupture is measured as the MBL.
