Trailer Weight and Tongue Weight Calculator
Works out gross trailer weight and the tongue weight it should carry, and checks both against the trailer, hitch and vehicle ratings.
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The formula
gross trailer weight = tare + load tongue weight = gross × tongue fraction
Tongue weight is the share of the trailer carried by the towing vehicle rather than the trailer axle. Around a tenth keeps the trailer stable; much less and the trailer steers the car, much more and it overloads the rear axle and the hitch.
What to watch out for
Tongue weight is the number that decides whether the trailer is stable:
- 10–15% of gross for a conventional trailer. European caravans with short couplings run 5–7%, with a noseweight limit on the car as well.
- Too little and the trailer sways — oscillation that builds with speed and is hard to recover from.
- Too much and the rear of the car squats, the headlights point up, the steering goes light, and the hitch and rear axle are overloaded.
Measure it with a tongue-weight scale, or a bathroom scale and a lever, after loading. Calculated figures assume the load is where you think it is.
Frequently Asked Questions
How much tongue weight should a trailer have?
10–15% of the gross trailer weight for a conventional trailer — 200–300 kg on a 2,000 kg trailer. European caravans run 5–7% and usually have a noseweight limit on the car of 75–100 kg.
What happens if tongue weight is too low?
The trailer sways. A small disturbance starts an oscillation that grows with speed, and once it exceeds what the car can damp, the combination jackknifes or rolls. It is the most common towing accident.
Does the trailer weight count toward my vehicle’s GVWR?
Only the tongue weight does — it is carried by the vehicle. The rest sits on the trailer axle and counts toward GCWR, not GVWR.