Trailer Tie-Down Load Rating Calculator

OK — effective WLL is at least 20% above cargo weight.

Marginal — effective WLL covers cargo but with under 20% headroom. Add another strap or step up rating.

Under — effective WLL is less than cargo weight. Add tie-downs, use higher-rated straps, or reduce load.

Invalid — cargo, tie-down count, or WLL is zero. Enter positive numbers.

Working Load Limit (WLL) is the maximum load a tie-down is designed to carry in normal use. It is what belongs in this calculator and is what is stamped on the tag.

Break strength is the force at which the strap or chain eventually fails in destructive testing. It is typically several times larger than the WLL. Never use break strength as your working number — a strap does not need to break to fail your load in transit.

If a tag is missing, unreadable, or shows only break strength, treat the strap as unrated and replace it before using it as a load-securing tie-down.

Total effective WLL = (tie-down count × WLL per tie-down) ÷ planning factor.

The planning factor lets you add margin for angled (indirect) tie-downs, worn straps, cold weather, or mixed-rating hardware. A factor of 1.0 assumes fresh, direct, straight-pull tie-downs. Many haulers use 1.25 to 1.5 when angles or wear are involved.

This tool does not model individual angles per strap, edge protection, or working-load derating for chain grade transitions. Use it to size a plan, then verify each anchor point and tag in the field.

Using break strength (or the number on the box) instead of the stamped WLL.

Assuming four straps automatically clear the load regardless of individual rating or angle.

Mixing chain grades or strap ratings without deriving the lowest common rating.

Ignoring worn stitching, cuts, or corroded hooks — a damaged strap is not at rated WLL.