What is the difference between light roast and dark roast caffeine content per myth?

The myth that dark roast coffee is more caffeinated is one of the most enduring pieces of misinformation in the coffee industry. It likely persists because dark roasts are often marketed as 'extra bold' or 'intense,' and consumers naturally associate these qualities with a higher caffeine content. However, the chemistry of the coffee bean tells a different story. Caffeine is a remarkably stable compound that does not degrade significantly during the roasting process.

The confusion is largely a result of how we measure coffee. Because dark roasts are roasted for longer, they lose more moisture and expand more than light roasts. This makes them less dense. If you measure your coffee by volume—using a standard scoop—you will fit fewer dark roast beans into that scoop than light roast beans. Therefore, if you brew by volume, your light roast cup will actually have more caffeine.

It is also important to consider the role of the roasting process in flavor development. As a bean is roasted, it undergoes chemical changes that create the bitter, smoky, and chocolatey notes we associate with dark roasts. These flavors are intense and can be very satisfying, but they are not an indicator of caffeine content. The 'strength' of a coffee is a subjective term that can refer to flavor intensity, caffeine content, or even the body of the drink, and these three things are not always correlated.

In practice, the best way to debunk this myth for yourself is to use a scale. When you weigh your coffee, you eliminate the density variable. You will find that 15 grams of light roast and 15 grams of dark roast provide a very similar caffeine experience. By focusing on weight rather than volume, you can enjoy your coffee with a better understanding of what is actually in your cup, regardless of the roast level you choose.