New to Vehicle Weights?

Take a minute to understand common weight terms, then use YWeight to plan, compare, and stay safe with your setup.

Why Understanding Weights Is Important

Towing a caravan or trailer isn't just about having a powerful vehicle — it's about safety, compliance, and confidence. Every vehicle and trailer has specific legal weight limits, and exceeding them can lead to mechanical failures, insurance issues, fines, and serious safety risks.

Whether you're planning a lap around Australia, buying your first van, or modifying your touring rig, understanding towing weights is essential.

Vehicle Weights

  • Gross Vehicle Mass (GVM)

    The maximum total weight of a fully loaded vehicle as specified by the manufacturer.
    This includes the vehicle itself, passengers, fuel, accessories, cargo, and tow ball download (when towing).

    Actual GVM typically indicates the actual measured weight of the vehicle.

  • Vehicle: Tare & Kerb Weight

    Tare Weight: The weight of the vehicle as it left the factory, with no passengers, cargo, or aftermarket accessories, but with minimal fluids (no fuel).

    Kerb Weight: The weight of the vehicle with standard equipment, full fuel, and necessary operating fluids, but no people or cargo.

  • GVM Actual - Hitched

    The actual weight of the vehicle when a trailer is hitched.
    It includes the tow ball mass transferred from the trailer to the vehicle, and can affect how close the vehicle is to its GVM.

  • Payload

    The maximum weight the vehicle can legally carry, calculated as:
    Payload = GVM – Kerb Weight
    Includes passengers, cargo, accessories, and tow ball mass when towing.

  • Gross Combined Mass (GCM)

    The maximum allowable combined weight of the towing vehicle and the trailer, as specified by the vehicle manufacturer.
    This includes:

    The fully loaded vehicle (up to its GVM),

    The fully loaded trailer (up to its ATM),

    And everything in or on both.

    Important: Even if both the vehicle and trailer are under their individual limits (GVM and ATM), you can still exceed the GCM, which would be illegal and unsafe.

  • Gross Axle Weight Ratings

    The maximum weight that can be safely supported by a single axle, as specified by the vehicle or trailer manufacturer.
    This rating includes the weight of the axle itself, wheels, brakes, suspension, and the load carried over that axle.

    Each axle—front and rear—will have its own GAWR, and neither should be exceeded, even if the vehicle is under its total GVM.

    ⚠️ Exceeding GAWR can lead to axle or suspension failure, reduced braking performance, and insurance or compliance issues.

Trailer Weights

  • Trailer: Tare Weight

    The empty weight of the trailer as specified by the manufacturer.
    Includes standard equipment but excludes any personal cargo, water, gas, or aftermarket additions.

    Important: manufacturers can have their own version of Tare Weight and may include some features other don’t. Ensure you confirm with the manufacture what is included in the claimed Tare mass.

  • Aggregate Trailer Mass (ATM)

    The maximum allowable weight of the trailer when fully loaded and unhitched, as set by the manufacturer.
    Includes the trailer's tare weight plus any load and the tow ball mass.

  • Payload

    The maximum weight the vehicle can legally carry, calculated as:
    Payload = GVM – Kerb Weight
    Includes passengers, cargo, accessories, and tow ball mass when towing.

  • Tow Ball Mass

    The downward force exerted by the trailer onto the vehicle's tow ball.
    Typically 8–15% of the trailer's total loaded weight (ATM).
    This value contributes to the vehicle’s GVM when towing.

  • Gross Trailer Mass (GTM)

    The maximum weight of the loaded trailer that is supported by the trailer’s axles only, when hitched to a vehicle.
    GTM = ATM – Tow Ball Mass

  • Gross Combined Mass (GCM)

    The maximum allowable combined weight of the towing vehicle and the trailer, as specified by the vehicle manufacturer.
    This includes:

    The fully loaded vehicle (up to its GVM),

    The fully loaded trailer (up to its ATM),

    And everything in or on both.

    Important: Even if both the vehicle and trailer are under their individual limits (GVM and ATM), you can still exceed the GCM, which would be illegal and unsafe.