The ZFW, or Zero Fuel Weight, is the weight of the plane itself (empty weight) plus the payload (cargo+pax).

The ZFW is put into the FMC as a XXX.X number, and is abbreviated by hundreds, SO,

empty weight (these are NOT real numbers, just examples) is 145,334LBS

payload is 32,029LBS, the total weight without fuel would be 177,363. Now, this would be put in as 177.4. You round up to the nearest hundred, and that becomes the number in the decimal place.

When the FMC yhas the ZFW, the fuel is automatically calculated, as well as a bunch of other valuable performance info.


I hope that helps!