Caravan Weight Guide – ATM, GTM & Tare
Towing safely starts with knowing your numbers. Your caravan has legally enforceable weight limits on its compliance plate, and your tow vehicle has its own limits. Exceeding either can compromise handling and braking, void insurance, and attract fines. The three figures you must understand are ATM (the caravan’s maximum loaded weight when unhitched), GTM (the weight carried by the caravan’s wheels when hitched), and Tare (the empty weight as it left the factory).
This guide explains how ATM, GTM and Tare relate to towball weight and payload, how to check them correctly at a weighbridge, and how to pack to stay within limits. With a clear grasp of these basics, you can set up your rig confidently and tow within the law.
If you’re new to towing, our caravan towing tips for beginners guide is a great companion read to this one.
Why Caravan Weight Matters
Exceeding your caravan’s weight limits can lead to:
- Dangerous handling and increased risk of accidents
- Excessive wear on your towing vehicle and caravan
- Voided insurance in case of an incident
- Hefty fines if caught during roadside inspections
⚠️ Consequences of Exceeding Your Caravan’s Weight Limits
- Insurance void — claims can be denied if the caravan was overweight at the time of an incident.
- Hefty fines — penalties for being overweight in WA can run into the thousands per offence.
- Loss of licence demerit points — overloading offences attract demerits in most states.
- Compromised brakes & suspension — premature failure of axles, bearings, brakes, and tyres.
- Dangerous handling — sway, jackknifing, and reduced stopping distance.
- Vehicle warranty void — exceeding tow vehicle limits can void manufacturer warranties.
Let’s break down these important weight specifications to help you tow with confidence.
Also Read: Essential Features to Consider When Buying a Caravan
Caravan Weight Terms at a Glance
| Term | Meaning | When It Matters |
|---|---|---|
| Tare | Empty weight from factory | Calculating payload |
| ATM | Max loaded weight (unhitched) | Total caravan limit |
| GTM | Weight on wheels (hitched) | Axle & tyre rating |
| Towball Weight | Weight pressing on tow vehicle | Vehicle towball limit |
| Payload | ATM − Tare | How much you can pack |
| GVM | Tow vehicle’s max loaded weight | Tow vehicle limit |
| GCM | Combined vehicle + caravan max | Whole-rig limit |
How the Weights Relate to Each Other
⚖️ Which Weight Means What
Tare Weight
Empty
As your caravan left the factory — no water, no gear, no gas.
ATM
Fully Loaded (Unhitched)
Maximum legal weight when standing on its own wheels and jockey wheel.
GTM
Loaded (Hitched)
Weight on the caravan’s axles only — towball weight transfers to the vehicle.
Key Formula: GTM = ATM − Towball Weight
ATM (Aggregate Trailer Mass)
ATM is the total weight of your fully-loaded caravan when it’s not connected to your vehicle. This includes:
- The caravan itself
- All your gear, water, food, and personal items
- Gas bottles and batteries
This figure is set by the manufacturer and can be found on your caravan’s compliance plate. It represents the absolute maximum weight your caravan can safely be when stationary.
Heavier components like dual gas bottles or upgraded battery banks can quickly eat into your payload — if you’re considering an upgrade to lithium battery systems, you’ll actually save weight compared to traditional lead-acid setups.
GTM (Gross Trailer Mass)
GTM refers to the weight that’s transmitted to the ground through your caravan’s axles when it’s connected to your tow vehicle. Simply put:
GTM = ATM − Towball Weight
This measurement is critical because it tells you how much weight your caravan’s suspension and tyres need to handle while you’re on the road.
Tare Weight
Tare Weight is your caravan’s weight when it leaves the factory — empty of personal items but including standard equipment. This typically includes:
- The caravan structure and chassis
- Standard appliances and fittings
- Empty water tanks
- Factory-installed options
The difference between your ATM and Tare Weight gives you your payload capacity — how much extra weight you can add to your caravan.
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Worked Example: How the Numbers Add Up
📐 Sample Caravan Calculation
Let’s say your caravan’s compliance plate shows:
- Tare Weight: 2,200 kg
- ATM: 2,800 kg
- GTM: 2,550 kg
Your payload capacity is:
2,800 kg (ATM) − 2,200 kg (Tare) = 600 kg of payload
Maximum towball weight allowed:
2,800 kg (ATM) − 2,550 kg (GTM) = 250 kg towball weight
What fills that 600 kg payload?
- Full water tanks (2 × 95L = 190 kg)
- 2 × 9 kg gas bottles = 18 kg
- Bedding, clothing, food = ~120 kg
- Tools, chairs, awnings, BBQ = ~80 kg
- Generator + jerry cans = ~50 kg
- Running total: ~458 kg — leaving only 142 kg of buffer!
Lesson: Payload disappears fast. Most caravanners are closer to their ATM than they realise.
How to Manage Your Caravan’s Weight
- Know your limits and familiarise yourself with all weight specifications for both your caravan and tow vehicle.
- Weigh your loaded caravan before trips at a public weighbridge.
- Pack strategically, placing heavier items low and over the axles.
- Consider water as a variable weight — each litre adds 1 kg.
If you’re regularly travelling with a heavy load, it’s worth checking your caravan’s suspension is rated for the job — see our caravan suspension services for upgrades and inspections.
💡 Pro Tip — The 10% Towball Weight Rule: For safe, stable towing, your towball weight should be roughly 10% of your caravan’s loaded ATM. Too little towball weight causes dangerous sway; too much overloads the rear of your tow vehicle. If your van weighs 2,800 kg fully loaded, aim for around 280 kg on the towball — and never exceed your tow vehicle’s rated limit.
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Weighbridge Tips
For accurate measurements, visit a weighbridge with your loaded caravan.
📋 Weighbridge Step-by-Step Checklist
- ✅ Load the caravan exactly as you’d travel — full water, gas, food, gear.
- ✅ Drive to a public weighbridge (most local councils or rural sale yards have one).
- ✅ Step 1 — Weigh the whole rig (vehicle + caravan, hitched). This gives GCM.
- ✅ Step 2 — Weigh the tow vehicle alone (caravan unhitched and off the bridge). Subtract from Step 1 to find GTM + towball.
- ✅ Step 3 — Weigh the caravan unhitched on the bridge with jockey wheel down. This is your ATM.
- ✅ Step 4 — Towball weight = ATM − GTM (or use a portable towball scale).
- ✅ Compare every figure against your compliance plate and tow vehicle specs.
- ✅ Keep the printed weighbridge ticket — useful evidence if you’re ever stopped.
Our service team at Rockingham RV Centre can help you understand your specific caravan’s weight limits and provide advice on weight distribution. We can also check your caravan’s suspension and braking systems through our workshop service to ensure they’re up to the task of handling your typical load.
Recommended Reading: Key Features to Look for in an Off-Road Caravan
Frequently Asked Questions
What happens if I exceed my caravan’s ATM?
Exceeding your ATM is illegal and carries serious consequences. Your insurance can be voided in the event of an accident, you can be fined by police or transport authorities, and you risk dangerous handling, brake failure, and chassis damage. It can also void your caravan’s manufacturer warranty.
How do I find my caravan’s ATM, GTM, and Tare?
All three figures are stamped on your caravan’s compliance plate, usually located near the drawbar or inside a cupboard. The plate is mandatory by law on all Australian-made and imported caravans. If your plate is missing or unreadable, contact the manufacturer or a certified workshop.
Can I upgrade my caravan’s ATM?
Sometimes, yes — but only if your chassis, axles, suspension, brakes, and tyres are rated to handle the higher weight. An ATM upgrade requires engineering certification and a new compliance plate. Speak to a certified caravan workshop before assuming you can simply increase the figure.
Does water count toward ATM?
Yes — every litre of water adds 1 kg to your loaded weight. A van with 200 litres of fresh water capacity carries an extra 200 kg when full. Many caravanners travel with partly empty tanks to save payload, then refill when they reach camp.
What’s the difference between GTM and ATM?
ATM is the total loaded weight of the caravan when it’s standing on its own (jockey wheel down). GTM is only the weight transferred to the ground through the caravan’s wheels when it’s hitched up — the rest (the towball weight) goes onto the tow vehicle. GTM = ATM − towball weight.
How much should my towball weight be?
The general rule is around 10% of your caravan’s fully loaded ATM. Too little causes dangerous sway, too much overloads your tow vehicle’s rear suspension. Always check both your caravan’s maximum towball rating and your tow vehicle’s maximum towball capacity — the lower of the two is your real limit.
Where can I weigh my caravan?
Public weighbridges are available at most local councils, transport depots, recycling centres, and rural sale yards across Western Australia. Many charge a small fee. You can also use portable towball weight scales (around $80–$200) for quick at-home checks.
Worried About Your Caravan’s Weight?
Our experienced team can check your suspension, brakes, and load capacity — or help you choose a caravan with the right specs for your tow vehicle. Browse our range of new and used vans, or book a workshop inspection today.
📍 89 Dixon Road, Rockingham, WA
Contact our team today to discuss your caravan weight concerns, or browse our range of new caravans and used vans if you’re considering an upgrade to a higher-capacity model.
James Groves is a caravan industry specialist and Managing Director of Rockingham RV Centre, a trusted WA-based caravan sales and repair business with more than 20 years of industry experience. James regularly shares practical advice on caravan maintenance, towing, servicing, and touring to help Australians travel safely and confidently.
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