Decaffeinated coffee has small amounts of caffeine in it, according to WebMD. FDA regulations require that coffee can only be labeled as decaffeinated if 97 percent of the caffeine has been removed from the coffee beans.
An average 12-ounce cup of coffee contains 3 to 18 milligrams of caffeine, according to Fox News. Ten different brands of 16 ounce drip-brewed coffee brands were tested in a study by University of Florida, which found that all of the brands contained anywhere from 8.6 to 13.9 milligrams of caffeine except instant decaffeinated Folgers Coffee Crystals. In the same study, a sample of Starbucks decaffeinated espresso drinks contained 3 to 15.8 milligrams of caffeine per shot, while a 16-ounce serving of brewed decaffeinated coffee contained 12 to 13.4 milligrams of caffeine.