23 CFR 658.17 · NHVR GML

Container road weight limit calculator

Load the box to what the truck can legally carry.

Enter the container, the truck tares and the axle layout to get the legal gross, the binding limit and the maximum cargo, with a drum or IBC count.

Last updated 2026-09-28. Math runs in your browser, no data leaves your computer.

The ship will take far more weight than the road will. A 20 ft box rated at 30,480 kg can be loaded to a figure no truck may legally pull on a US Interstate, so the road leg sets the real payload for dense chemicals.

Use the tare weights from the registration papers or a weighbridge ticket for the actual tractor and chassis. Every figure is gross, because the federal limits include all tolerances under 23 CFR 658.17(g).

Pick the country of the road leg, because the US rules work in pounds per axle and Bridge Formula while Australia works in tonnes per axle group.

The tare and rated gross fill in from the ONE dry container specs, so overwrite them with the figures on the CSC plate of the box you get.

Boxes of the same size vary by a few hundred kilograms with builder and repairs, so the plate figure is worth the walk to the door.

The box itself cannot carry more than its rated gross minus its tare, whatever the road allows, so the tool checks both.

Use the weight with fuel, driver and gear on board, since the roadside scale weighs the truck as it runs.

Take it from the chassis or trailer plate, because a tri-axle or extendable unit weighs noticeably more than a plain tandem.

A third chassis axle spreads the load but does not lift the 80,000 lb federal gross cap.

Read it from the tractor's axle rating label, because 23 CFR 658.17(f) holds the steer axle to the lower of 20,000 lb and that rating.

Measure from the steer axle centre to the rearmost chassis axle; FHWA's worked example rig measures 51 ft.

Measure from the first drive axle to the rearmost axle, since 36 ft or more lets both tandems carry 34,000 lb each.

Include the product, the package and its share of the pallet, and the drum and tote weight calculator gives that figure from the SDS density.

Before the booking, screen the name on the invoice. Shipment pre-check is on the paid plans, from USD 59 a month.

General guidance only. Verify against the cited primary sources before you commit to a shipment, declaration, or contract.

How the US limit is worked out

The legal gross is the lowest of four numbers. The first is the 80,000 lb cap in 23 CFR 658.17(b). The second is the Bridge Formula over all axles, W = 500 [LN/(N − 1) + 12N + 36], rounded to the nearest 500 lb as the FHWA guide does. The third is the Bridge Formula over axle 2 to the last axle, or 68,000 lb for two tandems spaced 36 ft or more. The fourth adds up the axle limits: the steer rating up to 20,000 lb, 34,000 lb on the drive tandem, and 34,000 lb on a chassis tandem or the Bridge Formula figure for a tri-axle group, capped at 20,000 lb an axle.

Cargo is that gross minus the tractor, chassis and container tares, and never more than the container's rated gross minus its tare. The axle total assumes the load is spread so every axle group reaches its own limit at once, which a real load rarely does, so a scale ticket per axle group is the final check.

How the Australian limit is worked out

The NHVR General Mass Limits take the lowest of the Table 1 figure for the vehicle, the sum of the axle group limits, and the reduced mass amount plus 1 t. For a 6 axle semitrailer with a standard steer axle that is 43.5 t, 44.0 t and 44.0 − 1.5 + 1 = 43.5 t, so 43.5 t applies.

Axle spacing limits in Schedule 1 section 5 of the Mass, Dimension and Loading Regulation are not modelled. The NHVR example shows 43.5 t for a 6 axle semitrailer with 10.0 to 10.5 m between the front and rear axles and only 37.5 t at 8.0 to 8.2 m, so a short combination needs the full table.

Worked example. A 20 ft box of IBCs loaded to the ship's limit

The booking. An importer books 20 IBCs of a caustic solution at 1,580 kg gross each, 31,600 kg in all, into a 20 ft box for a drayage run from Savannah on the Interstate. The box is rated 30,480 kg with a 2,150 kg tare, so the ship takes 28,330 kg of cargo and the forwarder trims the order to 17 totes at 26,860 kg, which looks fine on paper.

The failure. The trucker's tractor weighs 8,200 kg (18,078 lb) and the chassis 3,000 kg (6,614 lb). With the 2,150 kg box that is 13,350 kg of tare, and the 80,000 lb cap is 36,287 kg, which leaves 22,937 kg for cargo, only 14 totes. Seventeen totes put the truck 3,923 kg over at the scale. The choice is the usual one: take totes out of the box, or buy an overweight permit where the state allows it.

The fix. The importer books 14 totes per box at 22,120 kg and moves the rest to a second container. Gross comes to 35,470 kg, or 78,198 lb, under the cap with some margin for fuel, and the load clears the scale house.

Need to know how the drums or totes sit on the container floor once the weight is settled? The drum and IBC palletising calculator counts them by footprint.

Frequently asked

How much weight can a 40 ft container legally carry on US roads?

There is no fixed cargo figure, because the federal limit is on the whole truck. 23 CFR 658.17 caps gross vehicle weight at 80,000 lb on the Interstate System, so the cargo is 80,000 lb minus the tractor, the chassis and the empty container, and then only if the axles and the Bridge Formula allow it. Enter your own tares above to get the number for your rig.

What are the federal axle weight limits?

20,000 lb on any one axle and 34,000 lb on a tandem, under 23 CFR 658.17(c) and (d). Two consecutive tandems may carry 34,000 lb each when the first and last axles of the two tandems are at least 36 ft apart, which is the exception the FHWA Bridge Formula guide uses for the standard five axle tractor semitrailer.

How does the Federal Bridge Formula work?

W = 500 [LN/(N − 1) + 12N + 36], where W is the maximum weight in pounds on any group of two or more consecutive axles, L is the distance in feet between the outer axles of the group and N is the number of axles. FHWA rounds W to the nearest 500 lb. For axles 1 to 5 spread over 51 ft the answer is 80,000 lb, and for four axles over 35 ft it is 65,500 lb.

What are the General Mass Limits for a container truck in Australia?

The NHVR General Mass Limits page, amended for the HVNL changes from 1 August 2026, lists 43.5 t for a vehicle not otherwise mentioned and 44.0 t for a complying steer axle vehicle. The axle limits are 6.0 t or 6.5 t on the steer, 17.0 t on a dual tyre tandem and 21.0 t on a dual tyre tri-axle group, and the reduced mass amount and axle spacing limits can bring the total lower.

Do state limits change the answer?

They can, because states can hold grandfathered weights above the federal figures, issue permits for nondivisible loads, and set their own limits off the Interstate System, so a drayage move near a port can run under a different number. In Australia, notices and permits such as Higher Mass Limits sit outside General Mass Limits. Ask the trucker which limit the move runs under before you load to the figure here.

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Sourzi shows what official files say. It is not customs or legal advice. For a binding answer, ask a licensed customs broker, a CBP ruling or an Australian Border Force Tariff Advice.

File dates and links are on Data sources.