How Much Caffeine Is REALLY In Your Starbucks Order?

Is International Coffee Day a marketer-invented holiday created to sell coffee and greeting cards? Possibly. Should we still celebrate it? Absolutely. Though its origins aren't single-source, "National Coffee Day" was first observed in the U.S. in 2005; at a press conference for the New Orleans Coffee Festival in 2009, the Southern Food and Beverage Museum took the day "global" merely by announcing that the festival was, in fact, celebrating "International Coffee Day." Lo and behold, the grand tradition of chugging joe on September 29th was born. (How that makes September 29th different from any other day is unclear, but we'll go with it.)

You may already have known about today's holiday (and celebrated with a cup or five), but did you know exactly how much caffeine is in your beverage of choice — and how it works to perk you up? Caffeine occurs naturally in coffee beans and is structurally similar to adenosine, which is a neurotransmitter that lets us know we're tired. Caffeine binds to our adenosine receptors, which means adenosine itself can't latch onto these receptors. Without that adenosine, we feel more awake than we otherwise would — the more caffeine, the more alert.

So, how much of the stuff are you getting in your morning order? According to Caffeine Informer's database, Starbucks coffee has a notoriously high caffeine content: 330 milligrams in a 16-ounce (grande) black coffee, which Caffeine Informer rates as "extreme." Coffee Bean & Tea Leaf just barely edges out the 'Bucks, packing 333 milligrams of caffeine into every 16-ounce coffee serving. Peet's is also rated "extreme," serving up 267 milligrams of caffeine in a 16-ounce medium coffee. Dunkin' Donuts offers a milder lift: 203 milligrams of caffeine in every 16 ounces of its joe.