Over 50% of Americans drink coffee daily. The amount of caffeine a cup of coffee contains varies a great deal, depending on the strength of the particular brand of coffee, and the method of brewing -- which determines how concentrated the caffeine is. And, don't forget, the size of your coffee cup will also determine how much caffeine it contains.
The amount of caffeine you actually consume will depend, then, on the strength of your coffee, and the size of the cup. For example, a shot of expresso, the strongest type of coffee, contains about 50mg of caffeine per fl oz, but as a shot is only 2 fl oz, it would give you 100mg of caffeine, the same amount as an 8 fl oz cup of brewed coffee. Instant coffee is weaker at about 50mg per 8 fl oz cup.
The many different types of tea vary from containing high levels of caffeine, to herbal teas which contain no caffeine at all.
Regular tea, usually an Orange Pekoe or Black tea blend, contain about the same amount of caffeine as instant coffee -- 50 mg per 8 fl oz cup. But you can always steep your tea for longer, and get a stronger beverage, so the amount of caffeine in a cup of tea varies from about 20mg to 80mg per 8 fl oz cup.
There is some variation among different types of tea, with Chai ranging from about 60-120mg of caffeine per 8 fl oz cup, Assam black tea about 80mg per 8 fl oz cup, Earl Grey and Darjeeling teas containing average amounts of caffeine at around 50mg, Oolong having only 40mg, Green tea, 25mg, and White tea, 15mg.
The amount of caffeine in chocolate varies, according to the brand and the type of chocolate. On average, milk chocolate contains about 18mg of caffeine per 100g. That doesn't seem like much, but for a chocoholic, it can easily add up.
Dark chocolate contains much more caffeine, with dark chocolate containing upwards of 70mg of caffeine per 100g bar -- almost as much as you get in a cup of coffee.
Some manufacturers add extra caffeine to chocolate to produce a stronger caffeine hit -- typically around 100mg caffeine per piece, about the same amount as you would get in a shot of expresso coffee. Other types of caffeine-loaded candies, mints and gum are available.
White chocolate doesn't usually contain caffeine.
4. Soft Drinks
Soft drinks, typically marketed to kids, often contain rather a lot of caffeine. Cola is the most well-known source of caffeine, containing from about 30-60mg caffeine per 330ml can, depending on the brand. We are reminded of the similarity between cola and coffee by the distinctive brown coloring, so many parents make the mistake of thinking lemonade type clear soft drinks don't contain caffeine, although many of them do. Some contain the same amount as cola, or even more.
Iced tea and root beer are also common sources of caffeine, containing similar amounts to regular tea, often consumed in larger amounts. However, some brands of soft drinks do not contain any caffeine, or contain lower amounts, so it is worth checking the label to see.
5. Sports Drinks and Energy Drinks
Sports drinks and energy drinks are usually marketed in a way that emphasizes their caffeine content, although the actual amount of caffeine they contain varies greatly. Some contain about the same amount as tea or coffee, from 50-100mg caffeine per serving, while others contain much, much more.
Be careful with energy drinks which market themselves as "healthy" -- you can inadvertently consume a lot of caffeine if you don't check to label. Beware of glucose drinks, small print, and difficult to read labels.
Caution is advised when consuming high doses of caffeine, as it is possible to overdose on caffeine, for your blood pressure to rise, and even to develop mental health problems as a result of caffeine intoxication.