Originally Posted by 02Giant

There are several variables. What is the mixing ratio of the preferred paint? As an example Axalta Nason uses a 2:1 + activator, 8 oz of paint + 4 oz of reducer (+ 1/2 oz activator) gives you 12.5 oz sprayable. That is enough to paint a bike frame/fork/guard.
The gun set up makes a difference. A wide fan will waste paint on narrow tubes. The primer/sealer color vs the base coat makes a difference. If I am shooting a light color base I will seal with a light color and dark bases over dark sealers. The quality of the paint makes a difference, the Axalta Nason I mention takes more paint to cover than their Chromabase. The latter is more $$ though.