How close to empty am I?

Audi states 16.4 gallon capacity.  I was starting to shudder while driving uphill on the highway to the gas station when I filled up with 15.984 gallons.  I tend to fill up until the pump shuts off, and then to the next, or following, $0.25.  I suppose I could squeak some more gas in there, but it's not worth overfilling.