Its also worth considering the strength of the coffee may be more than anticipated. For instance, a 20oz cup of Starbucks coffee has _more than double_ the caffeine found in 20oz of red bull. It always gives me a laugh when the "5 hour energy" commercials advertise "only as much caffeine as a cup of the leading premium brand of coffee" -- aka Starbucks. A 5 hour energy _also_ has more caffeine than a red bull. I always bring this up in these conversations because it was all such a surprise to me.