What Is A Breaking Strength?

Breaking strength is determined by the maximum force or weight a product can withstand before the ultimate point of failure or the product breaks. In the cargo control industry having a breaking strength can help determine if the tie-down strap or chain is strong enough to hold your cargo safely in place.

Breaking strength ratings are commonly tested by using a tensile testing machine. This is also where the phrase tensile strength comes from.



The machine attaches each end of the tie-down strap or tie down webbing and pulls it until the product reaches the ultimate point of failure. At the ultimate point of failure the machine measures and records the amount of force in lbs to rate the product a breaking strength.

Even if a product has several components rated higher than the assembly breaking strength, it can only be rated as the weakest link in the entire assembly. Once the breaking strength rating has been recorded it can be used to determine the safe working load limit rating.

What Is A Working Load Limit?

A Working Load Limit (WLL) is the maximum weight or force a product can withstand before the ultimate point of failure or the product breaks divided by one-third. By using the breaking strength and dividing it by one-third the working load limit is designed to help ensure ultimate safety by creating a safety net to prevent the product from failing while in use.

A WLL helps to account for a sudden hard brake, a sharp corner, or a sudden jerk from rapid acceleration that may push the cargo control product you are using beyond its limits. This helps create a safety net to account for these situations and to prevent cargo from coming unsecured while on the road.

Working Load Limits can help determine if you need additional cargo control products such as tie-down straps or transport chains to hold the cargo in place. Working Load Limit (WLL) ratings are required in the cargo control industry and the labels must be visible and legible on all load securement products.

The Department of Transportation (DOT) requires all cargo control products used for load securement to have a visible and legible working load limit tag. Securing cargo without a WLL tag may be subject to penalties or fines depending on the violation.

Make sure to also check out our full blog post on What is a working load limit that goes further in-depth about how it was designed to keep you safe.

The Differences Between Breaking Strength and Working Load Limits

The major difference between breaking strength and working load limit rating is the margin for error. Breaking strengths do not allow for any margin of error, as they represent the ultimate point of product failure.

Working load limit ratings on the other hand have a margin of error built into the product rating to account for unknown strain and stress on the product you may encounter while on the road. This is why working load limit ratings are designed with a safety net.

Working load limit ratings also help prevent individuals and professionals from securing cargo heavier than the tie-down straps are safely rated for. We’ve created this chart below to help break down the major differences between breaking strength (BS) and working load limits (WLL).


At Trucking Depot, we have been a leading manufacturer of tie-down straps and custom tie-down straps in the United States since 1993. If you have any questions or need a product recommendation our experts would be happy to help. Reach us by calling 800-444-0956 or by using our Contact Us page at the top of the website if you prefer communications via email.

How To Calculate Working Load Limit Ratings

For example, if a ratchet strap had a breaking strength of 10,000 lbs and you used the working load limit rating formula of using one-third the working load limit rating of the ratchet strap would be 3,333 lbs WLL per ratchet strap.

You can find the working load limit rating by taking the breaking strength and dividing it by three parts. One part of this number is the safe working load limit rating as it is one-third of the breaking strength. Another example would be a 1,500 lbs breaking strength would be a 500 lbs safe assembly working load limit rating.

If you have any questions we would be happy to help and can be reached at 800-444-0956 or by using our Contact Us page if you prefer email communications.

How To Find The Working Load Limit Rating On Transport Chain

Transport chains such as 3/8-inch, 5/16-inch, or 1/2-inch are all stamped every 7th chain link with the grade of the chain.

For example, if the chain you are using is Grade 70 the chain will be stamped “G70” for short. Each grade of the chain has a specific working load limit rating and is required by the Department of Transportation (DOT) to be stamped.

This is very similar to the way that the tie-down webbing working load limit tags work and is designed to help keep other motorists safe and your cargo safely secured in place without worrying about it coming unsecured. It’s especially important to have a working load limit on the transport chain and binders as it is commonly used on open-air trailers where if the cargo comes unsecured it could fall off the trailer and toward other motorists.

The transport chain is ideal in conditions where metal machinery or sharp edges could damage the polyester tie-down webbing and cause it to fail. As the transport chain is made from high-quality heat-treated heavy-duty steel construction it’s a lot more durable and forgiving around metal edges than polyester webbing. As always, when selecting chain or webbing make sure to pair the safe working load limit rating up with the weight of the cargo you are transporting.