Tare mass vs kerb mass: what is the difference?
Tare mass and kerb mass are both "empty" weights, but they are not the same. Here is how the Australian Design Rules define each, and why the gap matters for payload.
Facts checked
The short answer
Both describe a vehicle with nobody in it and nothing loaded. The difference is fuel:
- Tare mass has only 10 litres of fuel in the tank.
- Kerb mass has a full tank.
Everything else is broadly the same. The gap between them is roughly your tank's capacity, less 10 litres, of fuel.
The ADR definitions
The Australian Design Rules (ADRs) set out the terms. In plain English, with the differences in bold:
- Tare mass is the vehicle ready for service, unoccupied and unladen, with all fluid reservoirs filled to nominal capacity except fuel, which is 10 litres only, and with all standard equipment and any options fitted.
- Unladen mass is the vehicle in running order, unoccupied and unladen, with all fluid reservoirs filled to nominal capacity including fuel, and with all standard equipment.
- Kerb mass is not defined separately. The ADR simply says "see Unladen Mass". Kerb and unladen are the same thing.
Why different sources quote different figures
You will see both figures in brochures, reviews and registration papers, and they are not always labelled clearly. A few reasons:
- Official sources define payload from different starting points. The ADR's term, load capacity, is GVM minus tare. Queensland's Department of Transport and Main Roads works payload out as GVM minus kerb. Both are reasonable. They just give different answers.
- Imported vehicles may come with European figures. The EU's "mass in running order" is a different measure again: fuel at least 90% full, plus a 75 kg driver. It is not the same as either Australian figure.
- The words get used loosely. Even official pages mix them. The NSW registration fees page, for example, describes tare as "(unladen)" weight, while the ADR uses "unladen mass" for the full-tank figure.
- Options change the number. Tare includes any options fitted, as in the definition above, so two vehicles of the same model can have different tares. A figure for one variant may not fit yours.
When a figure is not labelled, find out which one it is before you rely on it.
Why the gap matters
For payload
This is the first reason above in practice. If a payload figure is worked out from tare, it assumes 10 litres of fuel. Every litre above that is part of your load. Fill the tank and some of the advertised payload is already gone.
If it is worked out from kerb, the full tank is already counted. Comparing a tare-based payload for one vehicle with a kerb-based payload for another is not a fair comparison. See payload.
For GVM
GVM does not care which empty figure you started from. It is the limit on what the vehicle weighs as you drive it, with fuel, people, gear, accessories and the tow ball mass. Using a tare figure as your starting point and forgetting the fuel makes it easier to go over GVM without realising. See what is GVM.
Neither is what your vehicle weighs today
Both figures are for a vehicle as built. Neither includes a bull bar, canopy, drawers or anything else added later. Your real starting point is the vehicle as you use it, on a weighbridge (see how to weigh your rig).
Trailers and caravans have a tare too
A trailer's tare works a little differently. Like a vehicle's, caravan tare is the empty caravan with standard equipment and any options fitted, but it has water and wastewater tanks measured empty. After-market add-ons such as a TV, mattresses, extra gas bottles or an awning are not part of tare and count as load.
A caravan's tare is usually its weight as it left the factory, possibly before the dealer fitted extras, and trailer figures are generally less reliable than vehicle figures. If you are unsure, get it weighed. See ATM vs GTM.
Registration works with tare. In Victoria, for example, a trailer up to 4,500 kg must show its tare and ATM on its identification plate or the Register of Approved Vehicles, or a weighbridge docket stating the tare is needed if it was registered before.
Common questions
Is kerb weight the same as tare weight?
No. As in the short answer above, kerb weight (the ADR's unladen mass) includes a full tank of fuel and tare mass only 10 litres. Otherwise they describe the same empty, unoccupied vehicle.
Which figure should I use to work out payload?
As above, use your vehicle's actual mass as you drive it, weighed with its accessories fitted and your usual fuel. If you only have a published figure, check whether it is tare or kerb and adjust for the fuel.
Does kerb weight include the driver?
Not under the ADR definition, which is unoccupied. Some overseas measures, such as the EU's mass in running order above, include a 75 kg driver, which is one reason figures from different markets do not line up.
Where do I find my vehicle's tare?
Check the manufacturer's specifications for your exact variant, and ask your state road authority what it holds for your vehicle. A weighbridge gives you what your vehicle actually weighs.
Sources
Authorities
- Vehicle Standard (Australian Design Rule – Definitions and Vehicle Categories) 2005 — Federal Register of Legislation
- Safe Towing Guide — Department of Transport, Western Australia
- Caravans — Transport for NSW
- Vehicle registration fees — NSW Government
- Register a trailer or caravan — VicRoads
- Caravan Towing: towing at a safe weight (fact sheet) — Queensland Department of Transport and Main Roads
- Commission Implementing Regulation (EU) 2021/535, Annex XIII — EUR-Lex
Motoring associations (advice)