Aggregate Trailer Mass
The trailer’s maximum permitted mass when standing on its wheels and jockey wheel, uncoupled from the tow vehicle.
Understand the numbers before you tow.
Plain-English definitions, calculation logic and authoritative links for Australian towing. Use this guidance with the ratings for your exact vehicle and trailer.
DefinitionsATM, GTM, GVM, GCM and TBMHow calculations workWhat TowSmart estimates and comparesRules and sourcesCheck current official requirements
Towing definitions
Gross Trailer Mass
The maximum mass carried by the trailer wheels when coupled; towball load is carried by the vehicle.
Tare mass
The specified unladen mass. Included fuel, water, gas and accessories can vary—read the applicable definition and plate.
Available payload
The difference between a rated maximum mass and the relevant base or current mass.
Gross Vehicle Mass
The maximum permitted loaded mass of the tow vehicle, including towball download.
Gross Combination Mass
The maximum permitted combined mass specified for the tow vehicle and trailer combination.
Towball Mass
The downward load transferred from the coupled trailer to the tow vehicle.
Axle loads
The mass carried by each vehicle axle or trailer axle group; these limits still matter when GVM is acceptable.
Calculation explanation
TowSmart builds a loaded estimate.
It adds passengers, cargo, accessories, fuel and towball download to the vehicle; and cargo, accessories and water to the trailer. It then compares the result with the ratings entered or selected.
- Select or enter specificationsCatalogue values are reference data until confirmed for the exact variant.
- Configure the travelling loadWater and accessory positions inform the estimated towball effect.
- Review every marginA result within the entered limits is not certification and cannot account for every modification or legal requirement.
Regulations and authoritative sources
Towing requirements change and differ by jurisdiction. TowSmart does not replace a road authority, manufacturer, licensed weighbridge or qualified engineer.
Ready to build your combination?
Select your actual vehicle and trailer, then add the load you carry.