There is a common misconception about coffee's caffeine content.Some say light roast has more caffeine some say dark roast. I'm here to tell you that hey we're all wrong. No matter what the roast, caffeine actually remains acceptablly the same.
Here are the facts:

1. The Roasting Myth

Caffeine is a incredibly stable compound. It is highly resistant to heat and does not really burn off during the roasting process. Whether a coffee bean is roasted for a short time (light) or a long time (dark), the total amount of caffeine inside that individual bean remains pretty much the exact same.

2. Density vs. Weight

While the caffeine doesn't change, the physical size and weight of the coffee bean definitely do. As coffee beans are roasted, they lose water and puff up.

    Light Roast: Roasted for a shorter time. The beans retain more moisture, making them smaller and denser.

    Dark Roast: Roasted for a longer time. The beans lose a lot of moisture and expand, making them larger and lighter.

3. How You Scoop Matters

Because the roasting process changes the physical properties of the beans, the amount of caffeine in your morning cup depends entirely on how you measure out your coffee:
By Volume (Using a Scoop)

If you use a standard scoop to measure your coffee, light roast has more caffeine. Since light roast beans are smaller and denser, more of them fit into a single scoop. More beans per scoop = more caffeine per cup.
By Mass (Using a Scale)

If you use a digital scale to weigh out your coffee (e.g., 20 grams), dark roast has slightly more caffeine.
Because dark roast beans are lighter, it takes more physical beans to reach that 20-gram mark on the scale. More beans weighed = more caffeine per cup.