Weight Terms Explained

Confused by what the different weight terms mean for vehicles and trailers?  Here is a breakdown of the most commonly used ones and their meanings.

Unladen Weight

The weight of the vehicle (or trailer) when it is not carrying any persons, goods or items.  This normally does not include fuel, oils etc.

Kerb Weight

As above but normally includes a full tank of fuel, oils etc.  Some manufacturers may include the weight of a driver in their published kerb weight figures.


Gross Vehicle Weight / Gross Laden Weight / Permissible Maximum Weight

  • See MAM description below.


Maximum Authorised Mass

  • This is the maximum weight a vehicle or trailer can ever weigh safely when used on a road.  This should be displayed on the vehicle's VIN plate.  It includes its own weight plus all payload and carrying capacity.  If you exceed this, you will be breaking the law.
  • MAM is a more modern term now used for GVW / GLW / PMW / MTPLM.  It can also be referred to as "Maximum Allowed Mass".


Maximum Technically Permissible Laden Mass

This is another term for MAM most commonly used by caravan manufacturers / dealers.


Gross Train Weight

  • This is the total weight figure of the vehicle's MAM and the trailer's MAM when added together.  It can also be referred to as "Gross Combination Weight (GCW)".
  • This calculation is important for anyone trying to determine whether they are still legal to tow under a category B only licence. 

Nose Weight

Can also be referred to as Tongue Weight

  • The maximum static vertical load on the towing vehicle's coupling point for a trailer.

Here is a typical example of a vehicle's VIN plate.  It may also be displayed as a sticker on one of the vehicle's door pillars.

Take a look at the weights stamped in kgs -

2720kg  - Maximum Authorised Mass (MAM)

6220kg  - Gross Train Weight (GTW)

The last two weights refer to maximum axle weights -

1 = Front, 2 = Rear.

Calculating a vehicle's towing capacity from the VIN plate -

Using the VIN plate in the image, we can determine what this particular vehicle's towing capacity is by simply subtracting the MAM weight from the GTW weight.

  • In this case;  6,220 - 2,720 = 3,500kg
  • The maximum towing capacity of the vehicle this VIN plate belongs to is 3,500kg.

NOTE: - It has been known for V5 log books to be printed incorrectly. If in doubt, contact your local dealer and check the weights displayed on the vehicle's VIN plate itself (that's what the Police / DVSA Enforcement will use if you are stopped on the road).