Working Load Limit Explained in Plain Words
Load Safety Guide
Look at the tag on any strap or the stamp on any chain. You will see three letters again and again: WLL. Those letters stand for working load limit, and they may be the most important number on your truck.
If you get this number right, your cargo stays put and you pass inspections. If you ignore it, a strap can snap or a load can shift. This guide explains what the number means, where it comes from, and how to use it on a real load.
In This Guide
- What Is Working Load Limit?
- WLL and Break Strength Are Not the Same
- Where to Find the Number
- The Weakest Link Rule
- How Much Total WLL Do You Need?
- How Each Tie Down Is Counted
- Common WLL Numbers You Will See
- Things That Lower the Real Strength
- Simple Habits That Keep You Safe
- Frequently Asked Questions
What Is Working Load Limit?
The working load limit is the most weight a piece of tie down gear should hold during normal use. The company that makes the gear sets this number.
Think of an elevator
The sign inside might say it holds 2,000 pounds. The cable could hold much more than that before it breaks, but the sign gives you a safe number to follow every day. WLL works the same way for straps, chains, binders, hooks, and winches.
WLL and Break Strength Are Not the Same
Many people mix up these two numbers.
Break strength is the point where the gear fails. Makers test it by pulling the gear in a machine until it breaks.
WLL is a much smaller number. It is the break strength divided by a safety factor.
For most webbing straps, the safety factor is three. So a strap with a break strength of 10,000 pounds has a WLL of about 3,333 pounds. For chain, the factor is often four.
Why is there such a big gap? Because the road is rough. When you hit the brakes hard, take a sharp turn, or bounce over a pothole, the force on a strap jumps far above the normal weight it holds. The safety gap covers those moments.
Always plan your load with the WLL. Never plan with the break strength.
Where to Find the Number
- Straps. Look for a tag sewn into the webbing. It lists the WLL in pounds.
- Chains. Look for marks stamped into the links every few feet. A mark like G70 or G80 tells you the grade. The grade and the chain size together tell you the WLL.
- Binders. The WLL is stamped or cast into the handle or body.
- Hooks, shackles, and winches. The number is stamped on the metal.
If the tag is gone or the stamp is worn off, inspectors may treat that gear as the weakest type. A chain with no marks is rated like the lowest grade of chain. That is a good reason to replace gear with missing marks.
The Weakest Link Rule
A tie down is only as strong as its weakest part.
Picture a chain rated for 6,600 pounds hooked to a binder rated for 5,400 pounds. The whole tie down is rated for 5,400 pounds, not 6,600. The same goes for the anchor point on the trailer. If the D-ring is rated lower than the strap, the D-ring sets the limit.
Before you load up, check each part: the strap or chain, the hooks, the binder, and the anchor point. Use the lowest number.
How Much Total WLL Do You Need?
In the United States, the federal cargo rules use something called the aggregate working load limit. That is just the total of all your tie downs added together.
The basic rule is simple. The total must be at least half the weight of the cargo.
Example
Your load weighs 20,000 pounds. Half of that is 10,000 pounds. So your tie downs must add up to 10,000 pounds or more.
How Each Tie Down Is Counted
There is one more detail that surprises new haulers. Not every tie down counts for its full rating.
| How the Tie Down Runs | How Much It Counts |
|---|---|
| From one side of the trailer, over or through the cargo, and down to the other side | Full WLL |
| From an anchor point on the trailer straight to a point on the cargo | Half of its WLL |
| From the trailer, around the cargo, and back to the same side | Half of its WLL |
So a strap rated at 5,400 pounds counts as 5,400 pounds when it goes over the load from side to side. The same strap hooked straight from the trailer to the cargo counts as 2,700 pounds.
Back to the example. For a 20,000 pound load, four straps rated at 5,400 pounds each, run over the top from side to side, give you 21,600 pounds. That is well above the 10,000 pounds you need.
Meet both rules
The rules also set a minimum number of tie downs based on the length of the cargo. You must meet both rules, the weight rule and the count rule.
Common WLL Numbers You Will See
These are typical ratings. Always go by the tag or stamp on your own gear.
| Gear | Typical WLL |
|---|---|
| 2-inch ratchet strap | About 3,333 pounds |
| 4-inch ratchet strap or winch strap | About 5,400 pounds |
| 5/16-inch Grade 70 chain | 4,700 pounds |
| 3/8-inch Grade 70 chain | 6,600 pounds |
| 3/8-inch Grade 80 chain | 7,100 pounds |
You can compare ratings across the Safe & Tie straps collection and the chains and binders collection. Each product lists its rating so you can match it to your load.
Things That Lower the Real Strength
The number on the tag is for gear in good shape. Damage takes strength away.
- Cuts, burns, or holes in webbing
- Knots tied in a strap
- Bent, stretched, or cracked chain links
- Bent hooks or hooks that have opened up
- Straps pulled across a sharp edge with no edge protector
- Sun damage that makes webbing faded and stiff
If you see any of these, take that gear out of service. A new strap costs far less than a lost load.
Simple Habits That Keep You Safe
- Read the tag before every load.
- Match the binder to the chain. Do not mix a strong chain with a weak binder.
- Add one more tie down than the math says you need. Extra is cheap insurance.
- Use edge protectors on sharp corners.
- Check your tie downs early in the trip and at every stop.
Final Thoughts
Working load limit is not a hard idea. It is the safe weight for a strap, chain, or binder, set well below the point where the gear would break. Add up your tie downs, make sure the total is at least half your cargo weight, and use the lowest rated part as your guide. Do that on every load and you will haul with a lot more confidence.
Gear With the Rating Right on the Tag
Shop rated straps, chains and binders at Safe & Tie, shipped to 48 states.
Shop Cargo ControlFrequently Asked Questions
What does WLL mean on a strap?
WLL stands for working load limit. It is the most weight the strap should hold in normal use. You will find it printed on the tag sewn into the webbing.
Is WLL the same as break strength?
No. Break strength is the point where the gear fails in a test. WLL is much lower, usually one third of the break strength for straps, so you have a safety gap on the road.
Can I use a strap if the tag is missing?
It is not a good idea. Without the tag, nobody can prove the rating. During an inspection, gear with no marks can be treated as the lowest rating or cause a violation.
How do I work out how many straps I need?
Take the cargo weight and divide it by two. Your tie downs must add up to at least that number. Then check the length of your cargo to make sure you also meet the minimum count of tie downs.
Does a wider strap always have a higher rating?
Usually, yes. A 4-inch strap holds more than a 2-inch strap. Still, ratings vary by maker and hardware, so always read the tag on the strap you are holding.