How to use the Towing Capacity
- Enter GCWR, GVWR, kerb weight and the axle ratings from the door sticker.
- Add passenger and cargo weight.
- Enter trailer weight and tongue weight percentage.
- Check every limit; the lowest available margin governs.
How the calculation works
Maximum trailer weight = GCWR − actual loaded vehicle weight, where loaded weight is kerb weight plus passengers, cargo, fuel and tongue weight. Payload = GVWR − kerb weight, and tongue weight consumes payload directly. That is why the advertised maximum tow rating assumes a driver only and no cargo: add four passengers and gear and the usable figure drops by several hundred kilograms.
Tongue weight should be 10–15% of trailer weight for a conventional hitch and 15–25% for a fifth wheel or gooseneck. Too little causes trailer sway, which is a loss-of-control risk rather than a comfort issue; too much unloads the front axle and degrades steering and braking. Also confirm the hitch and receiver class rating, the rear axle rating, tyre load capacity at the pressures used, and trailer brake requirements, which typically apply above 1,500 kg. Reduce capacity for altitude and sustained grades, where cooling rather than torque becomes the binding constraint.
Max trailer = GCWR − (kerb + passengers + cargo + tongue) ; tongue = 10–15% of trailer weightSource: SAE J2807 tow rating framework and manufacturer GCWR/GVWR/payload definitions.
Worked example
GCWR 6,350 kg, GVWR 3,175 kg, kerb 2,450 kg, 340 kg of passengers and cargo, 2,700 kg trailer at 12% tongue weight.
- Tongue weight = 2,700 × 0.12 = 324 kg.
- Loaded vehicle = 2,450 + 340 + 324 = 3,114 kg, under the 3,175 GVWR.
- Combined = 3,114 + 2,700 = 5,814 kg, under GCWR.
- Payload used = 664 of 725 kg available.
Legal but tight — only 61 kg of payload margin remains, so extra passengers would exceed GVWR.
Frequently asked questions
Why can't I tow the advertised maximum?+
That figure assumes a driver only. Passengers, cargo and tongue weight all consume payload.
What is the correct tongue weight?+
10–15% of trailer weight for a conventional hitch; 15–25% for a fifth wheel.
What happens if tongue weight is too low?+
The trailer sways, which can cause loss of control at speed.
Do I need trailer brakes?+
Usually above about 1,500 kg, though the exact threshold varies by jurisdiction.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.