Recently, I have started to drink coffe more than in the past. One of the first things I noticed was that the a cappuccino from Starbucks is quite different than one from a place like Red Rock. Two things contribute to this difference; the first is the beans. The other? Size. This is what wikipedia has to say on appropriate sizing of a cappuccino:

embedly http://en.wikipedia.org/wiki/Cappuccino#Definition

In a traditional cappuccino, as served in Europe and artisan coffee houses in the United States, the total of espresso and milk/froth make up between approximately 150-180 mL (5-6 fl oz; 5-6 USfl oz).

The Starbucks tall is 12oz, and the venti is 20oz (venti literally means 20 in italian). But they have a little known size. “Short” weighing in at 8oz brings the right ratio of coffee to milk. So this is your pro-tip of the day: next time you are at Starbucks order that cappuccino as short.