Caravan weights are confusing because there are several limits and you must stay within all of them at once. Here they are in plain English. Then check your own compliance plates and your vehicle handbook.
The caravan weights
| Term | What it means |
|---|---|
| Tare | The empty weight of the caravan as built, without your gear, water or (usually) gas. Accessories added after manufacture are generally not included. |
| ATM (Aggregate Trailer Mass) | The maximum the caravan may weigh fully loaded, set by the manufacturer. RACV describes it as tare plus payload (RACV). |
| Payload | ATM minus tare: everything you can add, including water, gas, food, clothes and accessories. |
| GTM (Gross Trailer Mass) | The maximum weight on the caravan’s axles while it’s hitched. It’s lower than ATM because some weight sits on the towball. |
| Ball weight | The downward weight the caravan puts on the towball. Your vehicle and towbar each have a maximum ball weight. |
The tow vehicle weights
| Term | What it means |
|---|---|
| Kerb weight | The vehicle’s weight empty, with fluids and usually a partial or full tank of fuel (definitions vary by manufacturer). |
| GVM (Gross Vehicle Mass) | The maximum the tow vehicle may weigh loaded, including passengers, gear and the caravan’s ball weight. |
| Towing capacity | The maximum trailer weight the vehicle is rated to tow (with a suitable towbar). |
| GCM (Gross Combination Mass) | The maximum the vehicle and caravan may weigh together. RACV notes it’s illegal to exceed it (RACV). |
The rule that matters
Transport for NSW says the loaded caravan must not exceed any of the following: the towbar and coupling rating, the vehicle’s towing capacity and GCM, the caravan’s ATM, or the tyres’ load rating (Transport for NSW caravan safety guide). In practice, the lowest limit wins.
A worked example (illustrative numbers only)
Say your van’s plate shows tare 2,000 kg and ATM 2,600 kg, and your vehicle is rated to tow 3,000 kg.
- Your payload is 2,600 − 2,000 = 600 kg, before any add-ons fitted after delivery.
- Your limit is the ATM (2,600 kg), not the vehicle’s 3,000 kg, because it’s lower.
- You also still need the ball weight within the towbar and vehicle limits, the car itself within GVM, and the combination within GCM.
These numbers are only an example. Use the figures on your own plates.
How to check your real weights
- Find the caravan’s compliance plate (tare, ATM, GTM) and the vehicle’s figures in its handbook.
- Load up as you would for a trip: water, gas, gear and passengers.
- Use a public weighbridge: weigh the van on its own (ATM), hitched (GTM and axle load), and the vehicle with the van attached (GVM), then the whole combination (GCM).
- If you’re close to any limit, unload or redistribute and re-weigh.
If your rig is near its limits or modified, get advice from a qualified weighing service or your manufacturer.
Official sources
- Transport for NSW: Caravan safety (PDF)
- Transport for NSW: Caravan safety checklist (PDF)
- RACV: beginners’ guide to buying a caravan
- WA Road Safety Commission: “Give a Caradamn” checklist
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