Caffeine may as well be synonymous with “lifeblood” for the majority of adult humans. Making coffee or tea or cracking open a bottle of coke is often the very first thing people do in the morning, and certainly the first thing people consume. It's what people drink to convince themselves that they're functioning members of society, capable of answering an email or holding a conversation. But most people just know that they need it, not exactly how much caffeine is in the tea and coffee they're consuming in a day—or even in that first mugful. And there's a lot of confusion! Does tea have more or less caffeine than coffee? Is coke more caffeinated than coffee? Is Red Bull really the caffeine jolt it's cracked up to be? 

So many questions! And it's hard to be 100% definitive: Different brewing techniques can lead to differing caffeine amounts in coffee and tea. Plus, people respond to caffeine in different ways, thanks to a variety of factors. Certain medications can have an effect: A recent study showed that birth control pills inhibit the enzyme that breaks down caffeine, seriously upping the effect of that green tea latte. And, of course, genetics play a role—a variation in a gene called PDSS2 means some people process caffeine more slowly than others, which means they feel the effects of caffeine without consuming as much. Basically, a cup of coffee in one person can have little to no effect, while in another person, the same amount of coffee can keep them up for hours and make them feel like they're going to have a panic attack. (Would not recommend.)

The amounts of caffeine in different beverages aren't very well understood. Even at Extra Crispy, a lot of us had heard that black tea had more caffeine than coffee. That isn't the case. And you might assume that a drink like Red Bull, labeled an "energy drink," would provide a bigger jolt than your morning cafe au lait. (It doesn't—it only has half the amount of caffeine!—but the sugar may aid in that slightly manic feeling you get after you drink one.) You also may think that mellow green tea would have just slightly less caffeine than your Earl Grey—not quite. It has a full 30 milligrams less. Have you spent your whole life thinking that decaffeinated coffee or tea was devoid of caffeine? Sorry to tell you there's still a little, and it can still keep you up.

To help keep this in perspective, note that most medical professionals feel like 400 milligrams of caffeine is generally safe for healthy adults. So, that's nearly six 12-ounce black teas, or just shy of one-and-a-half 12-ounce coffees, or, like, nearly 12 12-ounce Cokes. (But maybe don't do that, for other reasons.) And, you know, maybe only drink half of that cup of that Black Insomnia coffee

To help you keep it all straight, check out our infographic below.