How does roast degree affect caffeine content?

The relationship between roast degree and caffeine is frequently misunderstood, often conflated with the loss of mass that occurs during the roasting process. As coffee beans roast, they lose moisture and organic matter, becoming more porous and less dense. A common misconception is that dark roasts are 'stronger' or contain more caffeine because they taste more intense, or conversely, that they contain less because the heat 'burns off' the caffeine. In reality, caffeine is a remarkably stable alkaloid. While some minor sublimation can occur at very high temperatures during extended roasting, the chemical concentration remains largely consistent across standard commercial roast profiles. The most significant factor influencing the caffeine in your cup is the extraction yield—how effectively your brewing method pulls solids from the grounds. Because dark roasts are more porous, they may extract more easily, but this is often offset by the fact that dark roast beans are less dense; if you measure by volume (scoops) rather than weight (grams), you are likely using less coffee mass for a dark roast than a light one, resulting in a lower total caffeine dose. For the producer, the focus remains on the inherent quality of the green coffee, as species (Arabica vs. Robusta) and agricultural practices dictate the baseline caffeine content far more than the roaster’s final profile. When evaluating caffeine, prioritize the weight of the dose and the efficiency of your extraction over the color of the bean.