Caffeine content

The stimulant effect of coffee is due to its caffeine content. The caffeine content of a cup of coffee varies depending mainly on the brewing method, and also on the variety of bean.[126]

According to an article in the Journal of the American Dietetic Association, coffee has the following caffeine content, depending on how it is prepared:[127]

brewed: 1 cup (7 oz, 207 ml) = 80–135 mg.
drip: 1 cup (7 oz, 207 ml) = 115–175 mg.
espresso: 1 shot (1.5–2 oz, 45–60 ml) = 100 mg

While the percent of caffeine content in coffee beans themselves diminishes with increased roast level, this does not hold true for the same coffee brewed from different grinds and brewing methods using the same proportion of coffee to water volume. The coffee sack (similar to the French press and other steeping methods) extracts more caffeine from dark roasted beans, while the percolator and espresso methods extracts more caffeine from light roasted beans.[128]
---------------------------- Light roast Medium roast Dark roast
Coffee sack - coarse grind .046------ .045------ .054
Percolator - coarse grind- .068 ------ .065------ .060
Espresso - fine grind------ .069------- .062 ------ .061