Towing Capacity Estimate

Free Towing Capacity Estimate calculator with clear step-by-step results.

About Towing Capacity Estimate

Towing capacity is the lowest of four independent limits, not the biggest number in the brochure. Gross combination mass minus the actual laden vehicle weight is often the binding constraint once the car is loaded, and the towbar or trailer axle rating can be lower than the vehicle's own limit.

Formulas

GCM headroom

Headroom = gross combination mass rating - actual laden vehicle mass

Governing limit

Maximum towable = the smallest of GCM headroom, manufacturer limit, towbar rating and trailer axle rating

Worked example

With the default values below, Towing Capacity Estimate returns Maximum trailer mass you may tow of 2,700.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Gross combination mass ratingminimum 100 kg: 6,000 kg
Actual laden vehicle massminimum 100 kg: 2,600 kg
Manufacturer braked towing limitminimum 0 kg: 3,000 kg
Towbar ratingminimum 0 kg: 2,800 kg
Trailer axle and tyre ratingminimum 0 kg: 2,700 kg

Results

Maximum trailer mass you may tow: 2,700.0 kg
Which limit governs: Trailer axle rating
Headroom under gross combination mass: 3,400.0 kg
Trailer mass as a share of vehicle mass: 103.8% %

Step by step

1Values used
2GCM headroom
3Governing limit
4Maximum trailer mass you may tow= 2,700.0 kg
5Which limit governs= Trailer axle rating
6Headroom under gross combination mass= 3,400.0 kg
7Trailer mass as a share of vehicle mass= 103.8 %

Assumptions and limits

The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Towing limits are legally binding and safety-critical. Verify every rating from the vehicle plate, towbar plate and trailer plate, comply with licence category requirements, and have the combination weighed when loaded.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Towing limits are legally binding and safety-critical. Verify every rating from the vehicle plate, towbar plate and trailer plate, comply with licence category requirements, and have the combination weighed when loaded.

Frequently Asked Questions

Why does loading the car reduce what I can tow?

Gross combination mass caps the total of vehicle and trailer. Every kilogram of passengers and luggage is a kilogram unavailable to the trailer.

What trailer-to-vehicle ratio is stable?

Guidance commonly suggests keeping the loaded trailer below 85% of the tow vehicle's kerb mass for stability, well below the legal maximum in many cases.