In a standard 8oz/225ml cup of brewed coffee you can expect to consume around 75 – 135mg of caffeine depending on the roast and type of coffee bean.
For example, lighter roasts tend to have more caffeine as they mostly maintain their size and natural caffeine content as opposed to dark roasts which shrink in size during the roasting process. You also need to factor in the type of coffee bean. Robusta coffee beans have almost double the caffeine content as Arabica beans.
It’s also interesting to note that espresso shots will have more caffeine per gram than brewed coffee whereas instant coffee has far less caffeine content per gram than any other coffee. Of course, decaf coffee has significantly less but despite it’s name, still has roughly 1 – 5 mg of caffeine per cup.
A 225ml cup of filter coffee will contain roughly 90mg of caffeine.
Instant coffee has slightly less caffeine than most of the other forms of brewing and contain around 60mg of caffeine per 250ml of coffee.
Cafetiere coffee has one of the highest caffeine contents of all coffees and is roughly 80 – 110mg per 250ml. This is due to the fact that the water stays in contact with the coffee grounds for longer than other methods and thus absorbs more caffeine.
A coffee made in a AeroPress yields a similar amount of caffeine as a cup of instant coffee at around 55 – 70mg per cup.
On a per ml basis, espresso has one of the highest caffeine contents due to the high pressure extraction that occurs during the brewing process. However, as an espresso shot is small in comparison to other forms of coffee, overall caffeine content lies somewhere between 60 and 65mg.
As mentioned above, despite its name, decaf coffee still contains caffeine. Depending on your brewing process, you can expect to find anywhere from 1 – 7mg of caffeine in your coffee.