Tiedown Calculator for Flatbed and Hotshot Loads

Enter the article's length, its weight and the working load limit (WLL) of your straps or chains. The calculator runs both federal tests and shows which one sets your count, so you know whether stronger gear or more tiedowns is the fix.

It's a quick check before you pull out of the shipper, not a full securement plan. Some cargo, like metal coils, logs and heavy machinery, has its own extra rules, covered further down.

How to use the tiedown calculator

1. Length. Measure the article itself along the trailer, in feet. Round up, not down.
2. Weight. From the bill of lading or the shipper's paperwork. If several pieces are bundled and secured together as one unit, you can treat the bundle as one article.
3. WLL of each tiedown. Use the rating marked on the strap tag or chain. If it isn't marked, use the federal default for its type and size (table below). If your straps differ, enter the lowest one.
4. Blocked? Choose yes only if a headerboard, bulkhead, other secured cargo or proper blocking stops the article from sliding forward.

The two rules, and where they come from

You need whichever number is higher. The full text is in Part 393, Subpart I of the federal rules, and the FMCSA cargo securement rules page links its Driver's Handbook, which explains the rules with drawings.

One detail changes the math. A tiedown counts at its full WLL only when it goes from the trailer, over or around the cargo, to the other side of the trailer. If it runs from the trailer straight to an anchor on the cargo, or comes back to the same side, it counts at half. The calculator assumes the full-count kind.

Default working load limits

When a tiedown isn't marked, these defaults from 49 CFR 393.108 apply. A manufacturer's marked WLL overrides the table. Unmarked chain counts as grade 30 proof coil, the lowest grade.

A tiedown is only as strong as its weakest part: the strap, the ratchet or binder, the hook or the anchor point on the trailer.

Worked examples

Made-up loads to show how the two rules interact. Each assumes full-count tiedowns.

Light, long loads are usually set by the length rule. Short, heavy loads are set by the WLL rule. The beam example shows why a headerboard matters: blocking saves one tiedown on the same load.

How to read your result

The answer is a legal minimum. Many experienced flatbedders add one, and many shippers require more than the rule. Steel and lumber shippers in particular often have their own written securement standards, so ask before you load. If you're choosing a first trailer, our guide on which trailer to buy first compares flatbed with van and reefer. Our flatbed securement basics guide covers edge protection, tarps and checks on the road.

Cargo with its own rules

The general rule isn't the whole story for some commodities. Part 393 adds extra requirements for:

• Logs and dressed lumber
• Metal coils and paper rolls
• Concrete pipe
• Intermodal containers and roll-on, roll-off containers
• Automobiles, and flattened or crushed cars
• Heavy vehicles, equipment and machinery
• Large boulders

Heavy equipment and machinery of 10,000 lbs or more needs at least 4 tiedowns, placed as close as practical to its front and rear, under 49 CFR 393.130. That's why the calculator adds a note for heavy articles.

If you haul any of these, read the section for that cargo before you load. A load that passes the general count can still fail an inspection on the commodity rule.

Common mistakes

• Counting a strap to the cargo at full WLL. It counts at half.
• Mixing strap ratings. If one strap is weaker, enter the weakest rating, or work it out by hand.
• Worn or cut straps. Damaged tiedowns don't count, and inspectors check.
• Forgetting to recheck. Federal rules require a check within the first 50 miles and again at set points on the trip. Loads settle and straps loosen. Plan the stops into your day, as our hours of service guide explains.
• Assuming the shipper's count is right. You're the one driving it. If it doesn't add up, fix it before you leave.
• Pricing the load before counting. Extra straps, tarps and time at the dock are costs. Make sure the rate still clears your floor from the cost per mile calculator.

Gear, loads and dispatch

Your securement kit decides which loads you can take. Tell your dispatcher how many chains, binders, straps and tarps you carry, and they'll book around it. Tarped loads usually pay extra, which our glossary calls tarp pay.

That's how our flatbed dispatch works, for a flat 6% of weekly gross. Hotshot carriers using gooseneck or dovetail trailers face the same rules. Our hotshot dispatch page covers the freight that fits those rigs, and the CDL calculator checks whether your rig needs a CDL. We don't book oversize loads.

This calculator covers the general federal rule for one article. It doesn't replace the commodity-specific rules or a shipper's own securement requirements.