Maximum Authorised Mass is the maximum weight the trailer is designed to carry when fully loaded. It is shown on the trailer's plate. You must never exceed this weight.

How do I weigh my trailer?

Use a public weighbridge (available at many industrial estates and farms). Alternatively, weigh individual items and add them up. Remember to include everything: cargo, water tanks, gas bottles, etc.

Does load distribution matter?

Yes, critically. Heavy items should be placed low and over the axle(s). A trailer that is rear-heavy can cause dangerous snaking. Aim for 60% of load weight over/forward of the axle.

How do I weigh my loaded trailer?

Take your loaded trailer to a public weighbridge (found at many recycling centres and commercial vehicle depots). Alternatively, use individual item weights and add them to the trailer unladen weight. Always include all contents, spare wheel, and accessories.

What is the difference between unladen weight and MAM?

Unladen weight is the empty trailer weight. MAM (Maximum Authorised Mass) or MTPLM (Maximum Technically Permissible Laden Mass) is the maximum the trailer can legally weigh when fully loaded. Never exceed the MAM as it is a legal limit.

CarCalcs

Trailer Weight Calculator

Calculate the total weight of your loaded trailer.

Trailer Unladen Weight

Cargo/Load Weight

Max Authorised Mass (optional)

From trailer plate

How We Calculate This

Simply adds the trailer's unladen weight to the cargo weight and checks against the maximum authorised mass (MAM).

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Actual figures may vary based on driving conditions, vehicle specifications, and other factors.