Towing Weight Calculator: Check Every Limit at Once
Enter your vehicle, towbar and trailer plate numbers plus your actual weights to see every limit pass or fail — for Australia, the USA & Canada, or the UK.
Example rig — replace every number with your own.
Towing weight check
Limited by Tongue weight vs hitch rating
assumes tow ball mass = 12.5 % of the trailer
Uses the numbers you enter from your plates and manuals — it can't check them for you. Weigh your loaded rig at a public weighbridge or CAT scale. Rules vary by state and country. Not legal advice.
A rig is legal and within the maker's limits only if every rating passes at the same time: the trailer against its own plate and your towing capacity, the tow ball (tongue) weight against the vehicle and towbar, the loaded vehicle (with the tow ball weight) against its GVM/GVWR, and the whole combination against its GCM/GCWR. Exceeding any one of them is enough to be overweight.
How to use this calculator
- Choose your region.
- Copy the ratings from your compliance plates, door label and manual.
- Enter actual weights from a weighbridge (best) or careful estimates.
- Read the red rows first — each shows how much you are over.
Worked example
Australian example rig:
How it's calculated
• GTM actual = laden ATM − tow ball mass (TBM)
• Vehicle coupled = vehicle actual + tow ball mass (TBM)
• Combined weight = vehicle coupled + GTM actual
• Towing capacity check = laden trailer vs lower of vehicle maker's towing limit and towbar rating
• Largest trailer = lowest of towing capacity, tow ball mass limit ÷ assumed %, GVM margin ÷ assumed %, and GCM margin
Frequently Asked Questions (FAQ)
Is the towing capacity the most I can tow?
Only on paper. The real limit is whichever rating you reach first; with a loaded vehicle that is often GVM/GVWR or GCM/GCWR, not the towing capacity.
Does tow ball weight count against my payload?
Yes. It is carried by the tow vehicle, so it counts toward GVM/GVWR and payload (WA Department of Transport guide; US motor home labels also state that tongue weight counts as cargo).
What tow ball weight should I aim for?
Follow your vehicle and trailer makers. As general guidance, the WA Department of Transport suggests about 8–10 % of ATM; GMC suggests 10–15 % for conventional trailers and 15–30 % for fifth-wheel/gooseneck trailers.
Where do I weigh my rig?
At a public weighbridge (AU/UK) or a CAT scale (US). Our weighbridge calculator turns the readings into the numbers this tool needs.
Sources
- RACQ — What you need to know about trailer and tow vehicle specifications
ATM, GTM, payload, ball load, towbar rating overrides, max towable = lesser of vehicle and towbar
- WA Department of Transport — Safe Towing Guide (PDF)
ATM, GTM, GVM (incl. hitch download), GCM, unbraked 750 kg, tow hitch download ≈ 8–10 % of ATM
- 49 CFR 571.110 (FMVSS 110) — Tire selection and rims; placard (Cornell LII)
Payload placard sentence; tongue weight counts as cargo
- GMC — Tongue weight
10–15 % conventional; 15–30 % fifth-wheel/gooseneck
- The Caravan and Motorhome Club — Buying a towcar
85 % / 90 % / never > 100 % guidance; MTPLM; gross train weight
- nidirect — Towing safety information
MAM, gross train weight on manufacturer's plate, > 750 kg needs brakes
- GOV.UK — Towing with a car
Licence rules information (rules differ by test date)
- 4X4 Australia — Towing vehicle weights explained
Secondary source: tare vs kerb definitions
Last reviewed: 2026-10-26
Built and maintained by Numberwright. The checks follow the definitions published by motoring bodies, transport departments and vehicle makers listed under Sources. Found a mistake? Contact details coming soon.
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