The amount of caffeine in a cup of coffee depends on how the coffee is prepared and whether or not it's decaffeinated. Decaffeination doesn't necessarily remove all of the caffeine.
A simply brewed, 8-ounce cup of coffee has 95 to 200 milligrams of caffeine. A brewed, decaffeinated cup has 2 to 23 mg. Single-serve, decaffeinated varieties of coffee have 2 to 4 mg. One ounce of restaurant-style espresso coffee contains 47 to 75 mg of caffeine. If it's decaffeinated, it has 0 to 15 mg.
Eight ounces of instant coffee contains 27 to 173 mg of caffeine. If it's decaffeinated, the caffeine levels drop to between 2 and 12 mg. A specialty coffee like a latte can contain between 63 and 175 mg of caffeine.