The darker the roast of the bean the lesser its caffeine content, because it is burnt off during the roasting process.  In general a coffee bean will contain the following caffeine content compared to weight: light roast, 1.37%; medium roast, 1.31%; and dark roast, 1.31%. This is per bean and the difference is slight, so it’s nothing to fret about.

Roast Levels

Where it does matter is when it is packaged and consumed. The longer the roasting process, the darker in color, lighter in weight, and larger in size the beans get. So if you measure by volume using a scoop, a darker roast coffee will contain less coffee grounds, will result in a weaker brew, and less caffeine content than a lighter roast. The best way to measure coffee for brewing is by weight where a “tablespoon” equals 7 grams. Regardless of roast level, this method will give you the most “full” cup. When measured this way, a darker roast will actually have more caffeine than a lighter roast. Why? Because caffeine content is proportional to the volume of coffee consumed.

One other factor to note is that Robusta coffee contains twice as much caffeine as Arabica coffee. And if you’re drinking a blend of both, it will have more caffeine than one that is 100% Arabica.

So to determine the caffeine content of dark roast vs light roast, we must consider the comparison by bean, by weight, by volume, or by coffee varietal.

Image Credit: Wise Coffee