One of the questions I get the most is, “Is it true that light roast has more caffeine?” My response? “Yep, that’s a very common myth.”
Wait…myth? Well, maybe not myth, but it definitely depends on how you look at it.
Caveat: Since we only sell Arabica beans on our website, we’ll only consider this type of bean. The other major type of bean, Robusta, simply isn’t as high quality of bean and doesn’t taste as good.
For all intents and purposes, all Arabica coffee beans have approximately the same amount of caffeine. That’s the short version.
Let’s get into the roast (and the science-y version). As the beans progress through the roast, the water content in the beans turns to steam and tries to escape. In doing so, the beans expand in size – the longer the roast progresses, the more the beans expand.
Because of this, darker roasted beans tend to be larger and as a result less dense than lighter roasted beans. So if you measure by volume – 1 tablespoon per 6 oz of water – there will be more coffee by weight of light roast coffee. This is part of why the ideal way to measure coffee is by weight. It ensures the same amount of coffee will be used regardless of which coffee you’re brewing. There are other reasons, but that will be another post.
TL;DR: Coffee beans all have about the same amount of caffeine, but a scoop of light roast coffee has more coffee – and therefore more caffeine – than a scoop of dark roast coffee.