GarageCalc A ratio is context, not an approval
Calculate ball weight share as measured ball load divided by the entire loaded trailer mass, multiplied by 100. For a fictional 2,000 kg loaded trailer with a 200 kg ball load, that is 200 ÷ 2,000 × 100 = 10%. This arithmetic does not establish a recommended target or certify stability.
Use the loading instructions supplied for the trailer and vehicle. Do not move cargo to chase an arbitrary percentage without checking those instructions and remeasuring the resulting axle and coupling loads.
Limits to check
- Vehicle manufacturer's maximum ball download and any configuration-specific loading conditions.
- Towbar, coupling and other fitted towing equipment ratings.
- The vehicle's actual loaded mass against GVM, plus each axle and tyre limit.
As a fictional payload example, a vehicle with 700 kg of available payload uses 350 kg of that allowance with a 350 kg ball download. The remaining 350 kg is a total-mass margin, not proof of rear-axle capacity.
Measure the travel load
- Load water, gas, luggage and accessories as they will travel.
- Use suitable rated scales following their operating instructions, or arrange a professional weighing service.
- Record loaded trailer mass, ball load and vehicle/trailer axle loads. Keep the loading configuration with the record.
- Repeat the measurements after a material loading change.
Mazda's BT-50 towing guide discusses ball scales and weighbridge checks. For equipment ratings and loading requirements, see NSW Government towing guidance. Checked October 25, 2026. Match any model-specific guidance to your vehicle.
The caravan weight calculator estimates mass and ball share; the caravan towing calculator compares four entered mass limits. Neither replaces loaded axle measurements.
Frequently asked questions
Does a 10 percent ball weight mean my caravan is safe?
A percentage alone does not establish stability or compliance. Follow the trailer and vehicle manufacturers' loading instructions, measure the loaded combination, and check the applicable vehicle, towbar, coupling and axle limits.
How do I measure ball weight?
Measure the trailer in its travel-loaded condition using suitable rated equipment and the equipment manufacturer's instructions. A professional caravan weighing service can help establish ball load and individual axle loads. An unladen specification is not a measurement of your packed trailer.
Does ball weight count against vehicle payload?
Yes. The download is carried by the tow vehicle and counts toward its loaded mass. Check actual axle loads as well as GVM; remaining total payload does not prove that the rear axle is within its limit.
My towbar and vehicle have different ball limits. Which applies?
Keep within every applicable limit and any manufacturer loading conditions. A higher-rated towbar does not raise the vehicle manufacturer's limit.