Determining empty weight of vehicle

I am trying to determine the empty weight of an old tanker truck. All I can find is the Gross Vehicle Weight Rating on the door panel. I'm trying to determine how much the vehicle would bring at a salvage yard and I have to know the empty weight to calculate. There are no papers on the truck. Is there a formula to determine empty weight or do you know of a web site that would provide that info? The GVWR is 27,000.

Thanks.

A very accurate (and free) way of doing it is to got to a gravel yard and drive it across their scales. Be sure to take out all your belongings and deduct your own weight from the value they give you. I founf them to be accurate to within 3 pounds.

[Robert Fogt]

For dry weight you also have to subtract the weight of the fluids. The oil, gas, coolant, etc.