Curb weight

Also called kerb weight, curb weight vs gross weight, empty weight, vehicle curb weight

Curb weight is what a vehicle weighs ready to drive but unloaded, fuel, oil and coolant at capacity with a full tank, nobody and nothing aboard, and it is the number subtracted from GVWR to get payload.

What is curb weight?

United States federal law defines it at 49 CFR 571.3, the same definitions section that carries the weight ratings: curb weight means the weight of a motor vehicle with standard equipment; maximum capacity of engine fuel, oil, and coolant; and, if so equipped, air conditioning and additional weight optional engine. The last clause reads oddly because it reads oddly in the CFR text itself. In plain terms: the standard vehicle, fueled, before anyone gets in or loads anything, and before options other than the two the definition names.

The full tank is the detail worth noticing. Gasoline weighs about 6.1 pounds a gallon, so a 32 gallon tank swings the scale by roughly 200 pounds between full and empty, and curb weight counts all of it. A vehicle weighed on fumes reads lighter than its curb weight, which flatters every calculation made from the reading.

Curb weight, gross weight, and the ratings

Four numbers get mixed together here, and two are measurements while two are limits. Curb weight is measured empty. Gross vehicle weight is measured now: the vehicle plus whatever happens to be in it, on a scale, today. GVWR is the certified ceiling for that total, and payload is the arithmetic between the other two: GVWR minus curb weight.

Which makes curb weight the quiet half of every payload argument. The rating is printed on the door label and never moves. The empty weight is wherever your build has pushed it: a steel bumper, a winch, sliders, drawers and a rack all ride along on every trip now, and every pound of them came out of the payload. The label does not know about any of it.