What is tow ball weight?

Tow ball weight – also called tow ball mass (TBM) or tow ball download – is the downward force the coupling of a loaded trailer or caravan applies to the tow vehicle's tow ball. It's not the trailer's total weight; it's just the portion of the trailer's weight carried by the ball, typically 8–15% of the trailer's Aggregate Trailer Mass (ATM).

What is a safe tow ball weight in Australia?

For most Australian caravans and trailers, a safe tow ball weight sits between 8% and 15% of the trailer's ATM, with around 10% considered the sweet spot for stability. Below 8% the trailer can sway; above 15% you risk overloading the rear axle and tow ball rating of the vehicle.

How do I calculate tow ball weight?

Multiply the trailer's loaded ATM by the desired percentage. For a 2,800 kg caravan at 10%, tow ball weight = 2,800 × 0.10 = 280 kg. Our calculator does this automatically and also flags whether the result is within your vehicle's maximum tow ball download rating.

Does tow ball weight reduce my vehicle's payload?

Yes. Tow ball weight sits on the rear of the tow vehicle, so it counts toward the vehicle's payload and GVM. A 280 kg tow ball download eats 280 kg out of your available payload before passengers, fuel and gear. Always cross-check with the payload calculator.

What's the difference between tow ball weight and ATM?

ATM (Aggregate Trailer Mass) is the total maximum weight of the loaded trailer when uncoupled. Tow ball weight is only the part of that weight transferred to the tow vehicle via the coupling – typically 8–15% of ATM for a balanced load.

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Tow ball weight calculator

Tow Ball Weight Calculator – Caravan & Trailer Ball Weight

Use this free tow ball weight calculator to work out the tow ball download (TBM) of your caravan, camper or trailer. We'll check whether it sits inside the safe 8–15% of ATM range, confirm it doesn't exceed your vehicle's maximum tow ball rating, and show how it affects your available payload. New to towing terms? Read understanding weights or jump to the full towing capacity calculator.