Load securement calculator: minimum tiedowns and working load limit

How many tiedowns: the rules the calculator uses

• Not blocked at the front: 1 tiedown for an article 5 ft or less and 1,100 lb or less; 2 if it is heavier or longer up to 10 ft; over 10 ft, 2 plus 1 for every extra 10 ft or part of it. Source
• Blocked at the front by a headerboard, bulkhead or other secured cargo: 1 tiedown per 10 ft or part of it. Source
• Heavy equipment of 10,000 lb or more: at least 4 tiedowns. Source
• Cars, light trucks and vans of 10,000 lb or less: at least 2 tiedowns, front and rear. Source

How much working load limit

The tiedowns together must have a working load limit of at least half the weight they secure. Source Not every tiedown counts in full: one that runs over the cargo from one side of the trailer to the other counts its full rating, while one attached directly to the cargo, or that comes back to the same side, counts half. Source A tiedown is only as strong as its weakest part, including the binder, hook and anchor point, and unmarked chain is treated as the lowest grade. Source

Worked example: a 24 ft steel beam EXAMPLE

A 12,000 lb steel beam, 24 ft long, sits on a flatbed with no headerboard blocking it. It needs 2 tiedowns for the first 10 ft and 2 more for the next 14 ft: 4 in all. The aggregate working load limit must be at least 6,000 lb. Four chains rated 5,400 lb each, running over the beam to the other side, give 21,600 lb, comfortably more. If the same four chains were hooked directly to the beam, they would count half, 10,800 lb, still enough here, but the difference matters on heavier loads.

Commodities with their own rules

The general minimums are only the start. Several commodities have specific sections that add requirements:

• Metal coils of 5,000 lb or more, with rules by coil orientation. Source
• Logs, with bunks, stakes and their own working load limit rule. Source See the logging truck guide.
• Dressed lumber and building products, with rules for stacked tiers. Source
• Cars and light trucks and heavy equipment, covered by the calculator. See heavy equipment hauling.

Blocking, bracing and friction mats

Tiedowns hold cargo down; blocking and bracing stop it sliding. A headerboard or bulkhead in front of an article lowers the number of tiedowns it needs, which is why the calculator asks. Friction mats under the cargo add resistance to sliding: a mat not rated by its maker counts as resisting horizontal movement equal to half the weight resting on it, under the same section that sets tiedown ratings. Source None of these replace the minimum count; they work alongside it.

Edge protection and strap care

A strap rated 5,000 lb is not rated over a sharp steel edge. Use edge protectors wherever webbing crosses a corner, and replace straps that are cut, burned, frayed or knotted. Inspect chains for stretched or cracked links, and binders for bent handles and worn hooks. Keep the tags readable, because an inspector who can't read a rating may treat the tiedown as the lowest grade.

What the result means

Green means your plan meets the federal minimum count and aggregate working load limit for the cargo type you chose. It doesn't mean the load is secure: chains must be tight, in good condition and placed where they actually hold the cargo, edges need protection where straps cross them, and anything that can shift needs blocking. Red means add tiedowns or use higher-rated ones. Recheck after the first 50 miles and at every stop; loads settle, and a chain that was tight at the shipper can be slack an hour later.

Securement mistakes inspectors find

• Worn, cut or knotted straps, and chains with damaged links.
• Binders or hooks rated lower than the chain, which lowers the whole tiedown's rating.
• Too few tiedowns on long loads, counted for the cargo's length rather than by guesswork.
• Loose tiedowns after the load has settled.

When you dispatch with us, we confirm the load's weight, dimensions and securement needs before we call, so you arrive with the right gear. See flatbed dispatch or send an application.