Understanding Chain Grades
What is Chain Grade?
Chain grades are a crucial aspect of determining a chain’s suitability for various applications, particularly in rigging and lifting. These grades are essentially indicators of the chain’s tensile or breaking strength.
Different Types Of Chains
Chain grades describe the ultimate breaking strength or tensile strength of a given type of chain. The common chain grades used today are G30, G43, G70, G80, G100, and G120. The numbers in each grade are newtons per square millimeter and one tenth of the actual mathematical grades. For example, G70 grade chains have a breaking strength of 700 N/mm2 (newtons per square millimeter).

Grade 30
These chains are general purpose and made from low strength carbon steel. They are commonly used for load securement in the agricultural, logging, and light construction industries.
Grade 43
Made from stronger carbon steel than grade 30 chains, grade 43 chains are used for towing, logging, securing containers, and marine applications.
Grade 70
Grade 70 chains are about 20% stronger than grade 43 chains and made from heat treated carbon steel that provides excellent strength and durability. They are commonly used for trucking and trailer tie downs, heavy load securement, and heavy towing.
Grade 80
Grade 80 chains are made of an alloy steel mixture that makes them extremely strong and suitable for overhead lifting. They can also be used for heavy duty towing, rigging, and tie downs.
Grade 100
With about 25% more strength than grade 80 chains, grade 100 chains are used primarily as a sling component for extremely heavy overhead lifting. They are also used for heavy duty rigging, towing, and construction applications.
Grade 120
A high-performance chain with unique square links and a higher strength-to-weight ratio than Grade 100. It’s less common and used for demanding overhead lifting applications.
Working Load Limit (WLL) of Chain
The other safety measure was identifying which types of chain are appropriate and strong enough for overhead lifting. Anytime we move or lift a load it is dangerous. Moving a load along the ground has the advantage that the ground is supporting the load. We have to overcome the coefficient of friction to move the load. The chain’s working load limit does not have to match the weight of the load. It needs to be able to handle the tension applied, which is based on the surface that it is being moved over plus some fraction of the weight of the load. This can be calculated using formulas.
How Do You Calculate A Chain Grade?
With several different ratings, you may be wondering: How do you calculate chain grades? A chain grade’s number or rating refers to the maximum stress it can handle per millimeter squared. If you were to make it a mathematical equation, it would look similar to the following:
Chain Grade = Maximum Tensile Force (Newtons)/Link Cross-Sectional Area (millimeters)2
Breaking down tow chain ratings using this equation, you could discover that a G70 chain can endure 700 Newtons per millimeter squared before bending, disfiguring, or breaking. Remember, the higher the grade, the higher the tensile strength is compared to the size of the chain links.
This equation works for nearly every chain on the chain chart until you get to chains that are designed with different materials. Carbon steel chains, like Grade 30, 43, and 70, cannot handle the stress/Newtons required for tasks such as overhead lifting. Meanwhile, alloy steel chains – like Grade 80 and higher – can handle that kind of tensile force and thus are recommended for any heavy-duty lifting.