Ever wonder why the guy who brings in Starbucks each morning seems to be about twice as perky as those schmucks toting plastic tumblers from Dunkin' Donuts or McDonald's? The answer: not all java is brewed equal. According to the chart above, one 16-ounce cup of Starbucks has more than 250 milligrams of caffeine—almost double the amount of its contemporaries.
Though the chart itself has some flaws—the numbers aren't adjusted to account for equal serving sizes, for instance—it allows you to make some simple guestimates about the effectiveness of your brand of go-juice. Most importantly, it tells you how many espressos (or Jolts or NOS's if want to be laughed out of the boardroom) it takes to turn counter productive; Jitters occur around 300 mgs. [Those interested in how tea stacks up, click here.]
Just remember that caffeine has about a five-hour half life, so sneaking out for that second coffee break the next time you have a case of the Mondays might actually make you feel more on edge.