Towing calculators

LoadGood App for towing and loading


The LoadGood calculator is ideal for understanding what you can add, remove or move in your car or trailer.  But, the spreadsheet  “Weighing your Car and Trailer” discussed on this page will help you collect necessary data and identify if you have a problem with your loads or what remaining capacity you have.

A Spreadsheet to Assist in Understanding Your Rig’s Compliance

The (very) basic limits and loads you need to be aware of and understand when you start your trip are:

  • weight of the car;
  • weight of the trailer; and
  • combined weight of the two.

You also need to know

But, to dig a little deeper, you need to also know the:

  • loads on all axles;
  • ball weight of the trailer on the car’s hitch; as well as the
  • percentage of the trailer’s weight that is imparted on the ball weight.  (Often this isn’t a make or break figure but it can be a good indicator).

Ignoring the percentage of ball weight on the hitch for a moment, your car and trailer has a stated manufacturer’s maximum limit for each of these figures.

These maximum figures have been determined with the engineers’ design in mind, the manufactures’ build considered and the individual components themselves. It’s not up to us mere mortals to say we can exceed these figures and drive off with disregard to, or blind uncertainty of these numbers.

Rest assured, if you and your rig are involved in any accident on the road, the police and the insurance companies will most likely be looking at these figures.

How Do I Find My Maximum Permissible Loads

Have a look in your glove box – under the tissues and broken pens you’ll probably find your Vehicle Owner’s Manual. Here, perhaps somewhere towards the back, you’ll find the specifications and maybe even a section on towing.

Otherwise, check on the Interweb or other reliable sources such as your automobile club.

Look for the modifications

Have a look too around the engine bay or inside the door panels to see if your car has had any vehicle modifications that will change your maximum loads. (eg Gross Vehicle Mass – GVM and Gross Combined Mass – GCM). Refer to Car and Trailer Loads Explained for an explanation of these terms – and more.

Towing and how the weights impact your towing ability and safety

Check the car’s tow bar

You will also need to check any stamps or plaques on the car’s tow bar, the actual tow ball hitch and the ball.  This will allow you to determine the maximum ball and trailer weights.

This will allow you to determine the maximum ball and trailer loads.

Your Trailer

Your trailer should have a compliance plate fixed to the draw bar or inside the door or one of the outside cupboards. This plate will provide the trailer’s Allowable Trailer Mass (ATM), Gross Trailer Mass (GTM) or load on the trailer axles.

For the purposes of this exercise, we don’t need to know the trailer’s Tare as this is an empty load, empty water-tanks, empty gas bottles, etc,  (and will never be seen again).

Loaded or Not Loaded

Within reason, my suggestion is to get your car and/or trailer weighed with a travel load on board. This way you will get a reasonable idea of what the load is that you have on board.

If the subsequent calculations reveal that you are within your rig’s capacity then perhaps that’s enough. If however, you’ve left out something important (like the dog or the kids) then you can calculate the loads and their impact using LoadGood calculator as discussed below and add these figures in later.

If however, you find you are exceeding your rig’s capacity in some way – DON’T PANIC just yet – have a look at what might be the be impacting items and see what that impact might be if they were to be removed or moved again using the LoadGood calculator as discussed below.

The next step is to get weighed. There are perhaps two simple ways that you can get your car and/or trailer weighed.

How to Weigh my Car and Trailer – Professionally

Now you are ready to go to a commercial weigh station (or have a mobile service come to you) who do these measurements for a fee. These services would usually present you with a detailed report at the end of the service that outlines how compliant your rig is in terms of the maximum capacities and capabilities of your car, trailer and setup.

For most mobile weigh station services, you’ll find that they will have numerous scale pads to put down on a level surface and have you drive your car onto them so that there is one under each wheel of the car and trailer and one under the hitch (when disconnected).

Another advantage for using the services of a mobile weigh station is that the individual scale pads will give you additional knowledge of the weights of both sides of the car and trailer.

They’ll use these figures to provide you with the report and any recommendations.

How to Weigh my Car and Trailer – Do It Yourself

The second method is where you do this yourself (and assume all responsibility).

Unless you have access to several scales and a level surface, you will need to front up to a weigh bridge (usually public) and progressively drive over the fixed scales to get reading that you can use to derive the necessary figures that will give a guide to your rig’s compliance.

The process I outline here is about as quick as you will get. But, be aware that individual weigh bridges may have their own system – so listen to their instructions carefully – they do it every day.

If you’re using the services of a council tip or scrap metal yard etc you will need to sweet talk the operator and ask nicely and perhaps  make prior arrangements.

Weigh bridges often use CB radio to communicate to users to read out the figures or tell you when to move forward. Follow their directions and be courteous.

Weigh Bridges

To do this, drive over the one set of scales as follows:

While the car and trailer are hitched take the following readings of the whole rig:

A1:  Weigh the car’s front axle – and move forward;

B1:  Weigh the car (front and rear axles) (GVM) – and move forward;

C:  Weigh the car (front and rear axles) and trailer (GCM) – and move forward; and

D:  Weigh the trailer (axle/s) (GTM) – and drive off.

With the trailer unhitched take the following readings of the car:

A2:  Weigh the car’s front axle – and move forward – and move forward; and

B2:  Weigh the car (front and rear axles) (GVM) – and drive off.

If you are wanting to only determine the loads in or on the car only determine A2 and B2.

Note: These figures are actuals that now need to be compared to maximum permissible amounts.

What Do I Do With These Figures?

Whether you have derived the figures yourself or through a professional weigh bridge you can now plug these figures into Camp and Travel’s “Weighing Your Car and Trailer” spreadsheet to determine how compliant your loads are.

You will find the Weighing Your Car and Trailer spreadsheet here 

Towing calculators
Note: Data can be entered as metric or imperial – just be consistent. 

Maximums – Here you enter the maximum permissible loads found from your car’s Owner’s Manual and compliance plates in the ochre coloured fields.

Actuals – This is where you enter the actual loads that you have weighed at the scales, as well as the distances where prompted. Again enter these in the ochre fields for both the car and trailer; and the car by itself.

Calculated Fields – As not all fields can be weighed on a roll-on-roll-off scales, calculated fields are provided here and will self-populate once you have populated all necessary fields.

Over / Under – On the right-hand side of the Weighing Your Car and Trailer Spreadsheet, a figure will be displayed which tells you how much tolerance you have between the maximum permissible figures you’ve entered and the actual loads recorded. If the value is negative (ie the maximum has been exceeded) it will be displayed as a red highlight.

What Do I Do if I Didn’t Include Something in these Weights

If you got weighed with only a few litres of fuel in the tank; without the kids, the dog or the packed esky in the back of the car, then simply use the LoadGood calculator as discussed below to determine how much needs to be factored into these loads.

It’s time to start planning THE trip.

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What Do I Do if I have Exceeded My Maximums

First things first – check your figures and be sure that you have understood the numbers and readings correctly.

Next – talk to your mechanic and trailer manufacturer to see how they have considered these figures in their design and build; and see what can be done to minimise your issues.

It may be too that a GVM upgrade on the car is your solution; or perhaps a GCM upgrade or a ATM / GTM upgrade to the trailer.

Or it could just be that you leave three cartons of beer behind and buy stuff when you get to your destination.

Look too at how and where you pack your travel gear. Perhaps three bicycles on the drawbar is too much to add to the ball weight.

Camp and Travel’s LoadGood Calculators can help as you record what items you want to move and where you want to move them to and see their potential effects.


LoadGood App for towing and loading


The results shown in these calculators are purely mathematically derived and do not take into account the many variances that can occur in the real world of cars, trailers, travel speeds and road conditions. As such, these calculators should be used only to determine what-if scenarios in the broadest sense and should always be followed up with actual weights taken at recognised weigh bridges. You are responsible for the loads you carry and for understanding the capacities and capabilities of your vehicle and trailer – and yourself. If in any doubt ask an expert in the relevant field.

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