We've seen the reported health benefits from drinking tons of coffee--over and over. However, most Americans aren't drinking coffee as a health food; they're drinking it for an alertness bump as they start their day. 

There's good science behind that too, as the U.S. military just leveraged a decade of research to determine exactly how much coffee you should drink, and when, to offset the lower alertness that comes with sleep deprivation.

Most of us are not brewing coffee in combat or at a remote military outpost, however. We've developed different habits. For many of us, those habits involve chains like Starbucks, McDonald's, or Dunkin' Donuts.

So, let's compare the chains. Or rather, let's pick up on the great work done this morning by intern David Wexner, at Quartz, who says he compared the relative levels of caffeine in coffee at the various chains, and then calculated things a step further by including the relative prices charged by each chain.

The truly surprising thing: While Starbucks has a well-deserved reputation for charging the most for a cup of coffee, it's actually one of the most economical choices
if you're calculating your purchase based on milligrams of caffeine per dollar.

There's actually a dark horse winner, however. Wexner, who is clearly worth whatever Quartz is paying him as an intern and then some, added it to his comparison of the three chains listed above on the highly scientific basis that all four "have locations within a block or two of the Quartz office in New York City."

Here are the results. We will start with the surprise winner. 


Surprise! Of all the chains Wexner looked at, 7-Eleven came out on top on the key metric of producing most economical human caffeine delivery system. Basically that means that a 16-ounce coffee at 7-Eleven will run you about $2.17 on the mean streets of Manhattan, and that cup will contain about 280 milligrams of caffeine. That works out to 129 milligrams per dollar, slightly better than the runner-up, which we'll look at next.


We already gave the ending away, but despite having the highest price for a 16-ounce cup of coffee at $2.65 (again: New York City), Starbucks came in with the highest dose of caffeine within those same 16 ounces, 330 milligrams. That works out to 124.5 milligrams of caffeine per dollar (mg/$).


By far the lowest price for a 16-ounce cup of coffee among the surveyed chains, McDonald's also had by far the least caffeine: just 145 milligrams. That works out to 121.8 milligrams per dollar. As you can see the difference in mg/$ among these top three wasn't radical, but it was enough to recognize.

Dunkin' Donuts

This one is also a surprise, and as a native New Englander I am not happy about it. Dunkin' Donuts had significantly less caffeine in a 16-ounce cup, about 240 milligrams, despite having the second highest price point: $2.39. That works out to an anemic 100.4 mg/$. 

So there you have it. If both drinking morning coffee and saving money are on your list of habits, the numbers are pretty clear. Of course there are other factors that might go into your choice like taste and convenience, to say nothing of "relative likelihood you'll wind up in handcuffs for asking to use the bathroom."

Next up: a study on whether the lower concentration of caffeine in Dunkin' Donuts coffee somehow effects the truly horrible driving habits we see in New England. I'd read that over a cup of coffee, anyway.