Strange that forever I have read the average cup of coffee has 100 mg of caffeine. But according to this stupid piece a full liter has 2 - 4mg of caffeine! I call the whole article into question with such sloppy reporting.
A cup of regular coffee can have anywhere from 25 to 500 mg. of caffein, depending on the type of coffee, how finely you grind it, and how strongly you brew it. Decaf coffee generally has 2 to 4 mg. of caffein.
Just checked:
8 oz coffee = 95 mg
12 oz Red Bull = 102 mg