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Privacy PolicyUse this free Australian towing weight calculator to understand how GVM, GCM, payload and front and rear axle limits interact with accessories, passengers, cargo and caravan towball load.
GVM, GCM and axle load limits are three of the most misunderstood figures in Australian towing and 4WD setup planning. The ClearPath calculator brings them together in one place so you can compare your supplied weights with the vehicle ratings you enter — and identify what still needs to be verified.
GVM (Gross Vehicle Mass)
The maximum permitted weight of the vehicle and everything in it — accessories, passengers, cargo and towball download combined.
GCM (Gross Combination Mass)
The maximum permitted combined weight of the vehicle and any trailer being towed. Towing at 3,500 kg doesn't mean you have 3,500 kg of payload left — GCM caps the total.
Axle Load Limits
Front and rear axles each have their own maximum load. A heavy rear accessory list or towball download can push the rear axle over its limit even when GVM is within range.
Where weight sits matters as much as how much there is. A 60 kg bullbar ahead of the front axle shifts load forward; a 100 kg canopy behind the rear axle shifts it back; a 350 kg towball download levers weight off the front axle and onto the rear. Exact changes depend on wheelbase and each load’s centre of mass. Use the accessory planner with measured distances or the detailed weight-distribution calculator with measured baseline axle masses. The basic payload checker does not establish axle loads.
Need to compare a specific vehicle and caravan before buying? Use the ClearPath vehicle and caravan tow match, or explore our Australian towing guides for plain-English explanations.
For a conventional caravan, the coupled vehicle mass includes the load transferred through the towball. Example: a travel-ready vehicle at 2,850 kg before coupling plus 280 kg towball load gives 3,130 kg. Against an entered 3,200 kg GVM, the calculated headroom is 70 kg. This is not spare capacity on each axle: front and rear ratings require separate checks.
Using the same example, a caravan weighing 2,800 kg in total gives a combination mass of 2,850 + 2,800 = 5,650 kg. Alternatively, coupled vehicle mass 3,130 kg plus trailer axle mass 2,520 kg gives the same 5,650 kg. Do not add the full caravan mass to the already-coupled vehicle mass: that counts the 280 kg coupling load twice. Against a 6,000 kg GCM, the indicated margin is 350 kg.
GCM minus actual vehicle mass before coupling gives a combination-based trailer allowance. GCM minus rated GVM answers a different loading scenario. Neither replaces braked towing capacity, towbar and coupling ratings, caravan ATM/GTM, axle checks or manufacturer conditions. Work through the actual intended load and each applicable ceiling.
A leverage calculation gives a change in axle load, not the total axle load. Add the calculated rear-axle increase to a measured, uncoupled, travel-ready rear-axle reading. Compare the result with the applicable rear-axle rating and verify the coupled setup by weighing. A GVM upgrade should not be assumed to increase GCM, tow rating or every axle rating; inspect the actual approval documentation.
Free tools help you understand individual checks. Choose the report that matches the decision you need to make.
Australian reference guidance: Queensland towing weights and vehicle selection, towing equipment and road authority guidance by state. Examples above are illustrative calculations. Verify the exact ratings and loaded weights for your setup. See our editorial methodology.
Calculations use manufacturer-published specifications and Australian road authority reference material, with vehicle details organised by model year, configuration and modification status.