By volume, espresso has the most caffeine, but since people usually have less espresso in an espresso drink (latte, cappuccino, frappe, etc) than they do when drinking cups of black coffee, they often consume less caffeine with the espresso drink. Does that make sense? If you were to drink a full coffee cup of espresso, it would have roughly 3 times the caffeine of brewed black coffee, in part because the method of making espresso extracts more caffeine than traditional brewing. Of the coffee beans themselves, there is little difference. Darker roasts actually have less caffeine by weight, because the roasting process eliminates some of the caffeine, and aribica beans have less caffeine that robusta.
at 2:24 PM on Feb. 15, 2009