Caravan Weights Explained
The lowest limit is the one that governs.
ATM, Aggregate Trailer Mass, is the most a loaded caravan may weigh. GVM, Gross Vehicle Mass, is the most your loaded car may weigh. GCM, Gross Combination Mass, is the most the loaded car and van may weigh together.
Every one of those limits applies at once, along with the tow rating and the towball limit.
Updated - specs from the manufacturer's own pages. 9 min read • Technical Guide
ATM is the most a caravan may legally weigh fully loaded and unhitched.
Payload is ATM minus Tare. Your car's braked tow rating, towball limit, GVM and GCM all bind at the same time.
- Tare - the empty weight (as the van left the factory)
- Payload - ATM minus Tare (everything you are allowed to add: water, gas, food and gear)
- Also apply at once - GCM, GVM, towball limit, towbar rating (the car's own limits, all binding at the same time)
The caravan's numbers
Tare, ATM and GTM (Gross Trailer Mass) are on the van's plate, often on the drawbar or by the door. Payload is ATM minus tare. Ball weight comes from the maker or a weighbridge, and it moves as you pack.
- Tare
- What the maker says the van weighs empty, with factory options and no water or gear. Later add-ons add to it.
- ATM (Aggregate Trailer Mass)
- The most the van may weigh, fully loaded. Compare it with your car's tow rating. The towbar and towball may be rated lower, and the lowest limit applies.
- GTM (Gross Trailer Mass)
- The most the van's own wheels may carry while hitched. It is lower than the ATM by about the ball weight.
- Payload
- ATM minus tare. Water, gas, food, gear and later add-ons all count.
- Ball weight
- How much of the van's weight presses on the towball. It changes with packing.
- GVM (Gross Vehicle Mass)
- The most your car may weigh loaded. People, luggage, accessories and the ball weight all count.
- GCM (Gross Combination Mass)
- The most car and van may weigh together.
Tare: the van with nothing in it
Tare is the van as approved, with its factory options fitted and its water tanks empty. Anything fitted later adds to it. It is the starting point for everything else, and brochures often lead with it. You will never tow a van at tare. Once the tanks are full and the fridge is packed, the van weighs more.
ATM: the most the loaded van may weigh
ATM (Aggregate Trailer Mass) is the maximum your loaded van is allowed to weigh when it is not hitched to the car. The manufacturer sets it based on the chassis, axles and suspension. A van over its ATM is overloaded, whatever the tow vehicle is rated for. ATM is also the figure to compare against your car's braked towing capacity.
Payload: what you can pack
Payload is ATM minus tare. It is your whole allowance for everything you add: water, gas, food, bedding, chairs, tools, the annexe and any extra battery. Water uses it fastest, because every litre weighs a kilogram. Fill two 95L tanks and you have spent 190kg before a single bag goes in.
Typical payload figures across the catalogue, how they differ by van type, and what eats the allowance fastest all live in caravan payload explained.
Water, gas and gear all come out of this 158kg.
See full specs →1,600kg of headroom leaves room for full tanks and touring gear. Weigh it loaded to be sure.
See full specs →Ball weight: the load on your towbar
Ball weight (also called towball mass or TBM) is the downward force the van's coupling puts on your towbar. Road authorities give guides of about 5 to 10 per cent (NSW) and 8 to 10 per cent of ATM (WA). Too little can make a van prone to sway. Too much can overload the car's rear axle and towbar. A maker's ball weight is often for the empty van. Loaded, it is usually higher.
Real example: the Fantasy Caravan Nano 15 publishes a ball weight of 200kg against an ATM of 2,000kg, about 10%. Your car, your towbar and your towball each have their own ball weight limit, and the lowest number in the chain wins. A 3,500kg towbar with a 350kg ball limit does not help if the car itself is only rated for 300kg on the ball. With the car loaded, the centre of the towball should sit 350 to 460mm above the ground. A towbar fitter can check it.
GTM: what the van's own wheels carry
GTM (Gross Trailer Mass) is the most the caravan's axles may carry when it's loaded and hitched to the car. Part of the van's weight sits on your tow ball, so at full load GTM works out to about ATM minus the ball weight.
Take a made-up van with a 2,500kg ATM and 250kg on the ball. Its GTM rating would be about 2,250kg. Weigh the van hitched with only its wheels on the scale, and compare that reading with the plated GTM. Release a weight-distribution hitch first.
GTM also sets the brake rules. Over 2,000kg GTM a van needs brakes on every wheel and breakaway brakes. Your car's limits are compared with the van's ATM and its loaded ball weight.
The car's numbers
Three more figures belong to your tow vehicle. They are in the owner's manual, in the towing and specifications sections. If a GVM or towing upgrade is fitted, its label and certificate carry the figures that apply.
Braked towing capacity
The headline number in most car ads. It is the heaviest braked trailer the manufacturer allows the car to tow. Your loaded van must not weigh more than it. Comparing the van's ATM with it is the simple check. The rating covers the van's own weight and everything packed in it, one total, which we unpack in does towing capacity include the caravan's weight. It is only a ceiling. The other limits below often cut it first.
GVM: Gross Vehicle Mass
The maximum your car may weigh fully loaded: people, fuel, luggage, accessories, and the van's ball weight pressing down on the towbar. Hitch up a van with 250kg of ball weight and you have used 250kg of the car's own carrying capacity. A bullbar, a fridge and a family can then put a dual-cab ute over its GVM.
GCM: the combined limit
GCM (Gross Combination Mass) is the maximum of car and van together. Many vehicles cannot be at full GVM and tow their full rated capacity at the same time, because the two added together exceed GCM. In a made-up example, a "3,500kg tow vehicle" loaded for a family trip might have only 2,800kg of towing left within its ratings. You get that figure by subtracting the loaded car's weight from GCM.
- braked towing capacity
- the towbar and towball ratings
- GCM minus your loaded car's actual weight
Our tow calculator checks a van against your car's tow rating, towball limit and GCM. Or start from your car with the Can I Tow It? flow and see which vans fit inside your car's tow rating, towball limit and GCM.
If someone has suggested a GVM upgrade as the fix for a tight sum, read GVM upgrades explained first. It raises what the car may weigh. GCM, the limit on car and van together, stays the same unless the certificate changes it.
The classic mistakes
Using up payload with water and gear
Every litre of water is a kilogram. The Kedron Caravans TE7 Triple Axle Topender carries 480L of fresh water. Filling those tanks uses 480kg of its 1,460kg payload straight away, before gas bottles, food, tools or a single camp chair. Two 9kg gas bottles add about 35kg with the steel. On a van with a small payload, pack lightly or travel with the tanks part full.
Checking the towbar but not the car (or vice versa)
The towbar has its own label, and the towball has its own stamped rating. An aftermarket bar rated to 3,500kg does not raise a car rated lower. A high car rating does not help if a lighter bar is fitted. Check the owner's manual, the towbar label and the towball, then work to the lowest number.
Believing the headline tow rating
Loaded car plus loaded van must stay under GCM (see section 2). For some utes and wagons, that puts the usable towing figure well below the brochure number. Do the sum with your actual loaded car weight, ideally off a weighbridge.
Comparing tare instead of ATM
Tare is the smallest weight figure, so it is easy to compare on. You will never tow the van at tare. Compare your car's tow rating against ATM, the fully loaded figure. Your packing still moves the ball weight and the car's load, so weigh the rig loaded.
Where the figures are, and what happens if you are over
Your van's plate carries its ATM, GTM and tare. Your car's tow rating, towball limit, GVM and GCM are in the owner's manual. A GVM or towing upgrade carries its own label and certificate. The towbar and towball carry their own ratings. Use the figures for your exact van and car, ahead of a model spec sheet. Our compliance plate guide shows where to find it and how to read it.
Penalties for towing overweight vary by state, and every state can fine you. After a crash, an insurer may look at whether the rig was over a rated limit. Read your policy's wording on overloading. Load the rig the way you travel and weigh it in three passes: hitched, then the car with the van hitched, then the van alone. Release a weight-distribution hitch before you weigh.
The public weighbridge finder lists weighbridges by state, so you can pick one on your way out of town.
Skip the spreadsheet
Pick your exact car and the tow calculator checks braked capacity, GCM and ball weight against any van on the site in one go.
Quick answers
What does ATM mean on a caravan?
ATM stands for Aggregate Trailer Mass. It is the most the caravan is rated to weigh fully loaded, including the part that rests on the towball. It is set by the manufacturer and stamped on the van's compliance plate. Your loaded van must never exceed it.
How do I work out a caravan's payload?
Payload is ATM minus Tare. Tare is the van's empty weight as it left the factory. The difference is everything you are allowed to add: water, gas, food, clothes, tools, bikes, the lot. Water alone eats payload fast because every litre weighs one kilogram.
Is ball weight included in the ATM?
Yes. ATM is the most the whole van may weigh unhitched, so it counts the weight on the jockey wheel. GTM (Gross Trailer Mass) is the most its axles may carry hitched. At full, evenly packed load, ATM is about GTM plus ball weight.
My car is rated to tow 3,500kg. Can I tow any van with a lower ATM?
Not automatically. Braked towing capacity is only one limit. GCM, GVM, the towball limit and the towbar and towball ratings all apply at the same time. Many 3,500kg-rated utes go over their GCM before the van reaches 3,500kg once the car is loaded. Check the owner's manual and do the sums, or use a tow calculator.
What are the legal caravan towing weights?
Every rated limit applies at once. On the van, that is the ATM (Aggregate Trailer Mass) and the GTM (Gross Trailer Mass). On the car, it is the tow rating, the towball limit, the GVM (Gross Vehicle Mass) and the GCM (Gross Combination Mass). The towbar and towball may be rated lower than the car's tow rating, and the lowest limit applies. A public weighbridge gives you the real weights to compare.
What happens if I tow overweight in Australia?
You can be fined and defected, penalties vary by state, and police and transport inspectors do weigh rigs at checkpoints. After a crash, an insurer may look at whether the rig was over a rated limit. Read your policy's wording on overloading. A public weighbridge gives you the real weights.