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Towing & Trailer Weights Calculator

Got a trailer or caravan? Want to know if your towing weights are within limits? This tool is what you need!

Just enter a few measurements below and you can:

  • Work out if your car can tow a given trailer or caravan;
  • See the heaviest trailer or caravan your car or 4×4 can tow;
  • Work out how much payload you have left once your trailer is attached;
  • See how close you are to limits such as GVM, max tow, payload and GCM;
  • Understand your trailer weights and get basic trailer weight advice;
  • Check front and rear axle weights, a common limit to run up against!
  • NEW as of 16/9/22 – added more calculations around axle loads after user demand.

The calculator assumes you are familiar with terms like GVM, GCM and TBM. If you’re not, then please read this first, then come back here.

You can use metric measurements or imperial, as the calculations are the same.

Calculator results are for guidance only – final checks should be made using all the data and limitations specific to your towcar and trailer which this calculator may not cater for.

Enter your trailer and towcar details below

For detailed explanations of the terms used in this calculator please read the help page
Your reference:

Whatever you want to name this calculation, e.g. "Ford Ranger and DreamVan". Not used in calculations. Only a-Z, 0-9 and - allowed.


Actual Trailer Weight Measure this; trailer ready to tow, including TBM; this should be equal to or less than the trailer's ATM.
Trailer ATM Maximum permitted weight of trailer; refer to trailer placard. The ATM should be equal to or more than the trailer's actual weight.
Towball mass (TBM) Measure this; as ready to tow. If you can't measure it, assume 10% of trailer weight. See TBM note in Help.


Towcar Unladen Weight Towcar's unladen weight, often known as kerb or tare, found on the car's specifications. Must be less than Actual Towcar Weight and GVM.
Actual Towcar Weight Measure this; towcar ready to tow but unhitched; accessories, modifications, luggage, people, fuel etc. This should be less than the towcar's GVM.
GVM Gross Vehicle Mass. Refer to your vehicle's weight placard or specifications.
Towcar TBM limit Towcar's maximum TBM. Look on towcar's placard, towbar, and tow tongue; use the lowest figure of the three.
Max tow capacity Refer to vehicle specs. Maximum braked towing capacity.
GCM Gross Combination Mass. Refer to vehicle's specs.

Rear axle limit data (optional)

Wheelbase Distance between front and rear wheel centres. Refer to vehicle's specs.
Overhang Distance between rear wheel centre and towball. You will need to measure this.
Rear axle load limit Maximum load on rear axle. Refer to vehicle's specs. Use 0 if not known.
Front axle load limit Maximum load on front axle. Refer to vehicle's specs. Use 0 if not known.
Weight on rear axle Measure using scales when towcar ready to tow but not hitched up, or use 60% of total weight as a guess.

If you have questions, comments or feedback please post them on the help page, after you’ve read it and the explanations 🙂

You may also like to try the Tyre Size Calculator.

The calculator and the information provided is free to you but cost me to produce and maintain, so please consider supporting me on Patreon and YouTube. In the last two years more than 160,000 calculations have been made by over 33,000 people!

Sponsorship welcome so long as independence is maintained.