A Kerb Weight in Tonnes, a Towing Table in Pounds
The caravan brochure says the van has a maximum laden mass of 1.6 t. The tow vehicle's owner's manual, printed for the North American market, lists a towing capacity of 7700 lb and a payload of 1580 lb. Before anything gets hitched up, those figures have to meet on one scale, and the only thing standing between them is a factor of 2204.62262.
This is a routine problem for anyone importing a vehicle, shipping a trailer across an ocean, reading a European road sign with an American plate on the door pillar, or simply comparing two spec sheets written on different continents. The ratings themselves are legal limits, not suggestions, so getting the arithmetic right is the cheap part of doing it properly.
Why One Vehicle Has Two Sets of Numbers
Brochures follow the market
The plate on the door pillar
Trailer labels rarely match the tug
Class names that stopped meaning weight
Reading a Rating Plate Against a Spec Sheet
Work one rating line at a time and write both units down; a mixed list is what leads to an overloaded axle.
Enter the tonne figure from the plate
Put the metric rating in the left field and pounds appear straight away, with no button in between. Decimal commas work as well as dots and stray spaces are ignored, so a plated 3,5 reads correctly.
Turn a US spec back into tonnes
Type the pound rating into the right-hand box instead, or press the swap button (↔) to flip the pair, when the manual is American and the road signs are not.
Switch to kilograms for the small lines
Tongue weight, roof load and towball limits are quoted in kilograms rather than tonnes. Search either dropdown for kilogram and the same page handles a 75 kg noseweight as easily as a 3.5 t gross figure.
Copy each result into your weight sheet
The copy button hands over the bare number, without a unit and without thousands spacing, so a spreadsheet of ratings stays numeric and can be totalled. Ctrl + C inside a field behaves the same way.
Vehicle and Trailer Rating Lines in Both Units
Typical figures for common classes, given as a sense of scale rather than as anything to plan a load against. Your own vehicle's plate always wins — options, drivetrain, body style and cab configuration all move these by hundreds of pounds.
| Vehicle or rating line | Typical tonnes | Same in pounds | What the number describes |
|---|---|---|---|
| Compact hatchback, curb weight | ≈ 1.2 t | ≈ 2650 lb | Empty and fuelled, before people or luggage |
| Mid-size SUV, curb weight | ≈ 2.0 t | ≈ 4400 lb | Already heavier than the "one ton" the name suggests |
| Half-ton pickup, curb weight | ≈ 2.3 t | ≈ 5100 lb | The empty truck alone is over two tonnes |
| Half-ton pickup, GVWR | ≈ 3.1 t | ≈ 6800 lb | Maximum loaded weight of the truck itself |
| Three-quarter-ton pickup, GVWR | ≈ 4.5 t | ≈ 10 000 lb | The upper edge of US Class 2b |
| Mid-size travel trailer, GVWR | ≈ 3.4 t | ≈ 7500 lb | Loaded trailer, hitch weight included |
| Box truck, US Class 6, GVWR | ≈ 11.8 t | ≈ 26 000 lb | The threshold where US licensing rules change |
| Class 8 tractor-trailer, federal gross limit | 36.3 t | 80 000 lb | US interstate maximum without a permit |
Follow the pickup rows and the naming problem is plain. A half-ton truck weighs more than two tonnes empty, is rated to about three loaded, and the half-ton in its name corresponds to nothing on the plate. Follow the trailer row instead and a different point emerges: a 3.4 t travel trailer needs a tow rating well above what a family SUV of 2 t offers, no matter how comfortable the combination feels on a flat road.
What Helps at the Hitch
Live figures while you read the manual
Every keystroke updates the other field, so a page of ratings can be converted one after another without touching a button.
Either direction, same page
Both fields take input and the swap control reverses them, which suits a metric trailer parked behind an imperial tow vehicle.
Kilograms for the smaller limits
The searchable dropdowns list all 18 weight units, so noseweight and roof-rack limits in kilograms sit in the same workflow as the gross figures.
Numbers ready for a load sheet
Copy returns digits only, so a column of converted ratings can be added up and compared against the plate without cleaning anything first.
Towing and Weight-Rating Questions
Curb weight, GVWR, payload and GCWR — what is the difference?
Curb weight (kerb weight in British usage) is the vehicle as it stands empty with fluids and fuel. GVWR is the maximum the loaded vehicle may weigh, so payload is simply GVWR minus curb weight, and it has to cover passengers, cargo, accessories and the trailer's hitch weight all together. GCWR is the ceiling for the tow vehicle and trailer combined; the advertised towing capacity is what is left of the GCWR once the truck itself is accounted for, usually assuming a driver and nothing else on board. Load four adults and their bags and the real towing headroom shrinks even though the brochure number has not changed.
Why does a "half-ton" pickup carry far more than half a ton?
The name is an inherited class label, not a specification. Mid-century light trucks really were rated at roughly 1000 lb of payload, and the half-ton, three-quarter-ton and one-ton names came from that era. Chassis, brakes, suspension and tyres have improved out of all recognition since, and a modern half-ton commonly carries 1500 to 2000 lb, with some configurations higher still. Manufacturers kept the old names because buyers recognise them, so they now function like clothing sizes: they tell you which bracket of truck you are looking at and nothing whatever about its actual capacity. Read the plate.
How much weight should the trailer put on the hitch?
For a conventional bumper-pull trailer, the usual guidance is 10 to 15% of the loaded trailer weight on the coupling — so a 3.4 t (7500 lb) trailer presses down with roughly 340 to 510 kg, or 750 to 1100 lb. Gooseneck and fifth-wheel trailers run higher, around 15 to 25%, because the load sits over the rear axle. Too little and the trailer starts to sway at speed, which is the dangerous failure mode; too much and the tow vehicle's steering goes light at the front. That downward force is also part of the tow vehicle's payload, which is where many otherwise-legal combinations quietly go over. European caravans work to a similar principle but the towball limit is normally an absolute figure in kilograms, often 75 to 100 kg.
Can an axle be overloaded while the gross rating is still fine?
Easily, and it is one of the most common ways a load fails an inspection. Each axle carries its own GAWR, and the two axle ratings usually add up to more than the GVWR, which tempts people into thinking there is slack. What matters is where the mass sits: pile everything behind the rear axle, or hitch a heavy tongue, and the back axle can pass its limit while the total is still comfortably under the gross. The lever works both ways, since weight hung behind the rear axle lifts load off the front. The only way to know is a weighbridge that reports axle by axle, or a public scale used one axle at a time.
How do road weight limits compare between tonnes and pounds?
They are set by separate rulebooks, so the numbers land in different places. The US federal interstate limit is 80 000 lb gross, which is 36.3 t, with 20 000 lb (9.1 t) on a single axle and 34 000 lb (15.4 t) on a tandem, plus a bridge formula that also depends on axle spacing. Much of Europe works to 40 t on the same kind of route, rising to 44 t for some intermodal movements — noticeably more gross weight, spread over more axles. Local restriction signs are what most drivers actually meet: a British 7.5 t plate is 16 535 lb, and a 3.5 t weight restriction is 7716 lb, which catches large pickups and motorhomes that would pass unremarked at home.
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