Light, medium, dark roast: understanding roast level

A green coffee bean has neither the taste nor the smell of coffee. It acquires them with heat. The bean first loses its water, then browns: this is the Maillard reaction, where sugars and proteins react together and create much of the aroma and the brown colour. At first crack (around 200 °C according to several guides), steam and pressure make the bean burst with a sound close to popcorn: the development phase begins, where taste changes fast. If roasting continues, a second crack follows (around 225 to 230 °C according to the same guides): oils rise to the surface and roast notes take over. The roaster chooses where to stop the heat. That stop is the roast level. Exact temperatures vary with machines and sources: remember the order of events, not the number.

Roughly, a light roast stops around or just after first crack, a medium roast between the two cracks, a dark roast at second crack or beyond. But these boundaries are blurry: the words are not standardised, and each roaster defines them their own way. One roaster's 'medium' can be another's 'light'. The only objective reference is a colour measurement, Agtron: the higher the number, the lighter the coffee. Coffee Review, which scores coffees, uses it to define its levels. Few bags show it; mostly, remember that these words describe a continuum, not boxes.

Coffee beans lined up in a grid on a beige background, in varied shades of brown, like a roast colour chart

On the same origin, the more you roast, the more roast flavour takes the place of the flavour of the origin. With a light roast, beans are light brown, without oil, and the cup is generally livelier: marked acidity, fruity or floral notes, a lighter body. With a medium roast, acidity is more balanced, body fuller, and differences of origin remain visible. In medium-dark, fruit turns toward chocolate, a slight roast bitterness appears and acidity fades; in dark, bitterness becomes distinct, notes of burnt wood or smoke can dominate and the character of the origin disappears. Careful: 'acidic' does not mean 'under-extracted'. In a light coffee, acidity is part of the profile. If a light cup tastes sour to you, the problem may lie in extraction more than in roast level: our article on coffee that is too bitter or too sour helps you tell them apart.

'Dark is stronger' mixes up two things: the intensity of roast flavour (yes, more present) and the amount of caffeine, on which the sources we read do not agree. A Sprudge article (2019), based on a lab study carried out at Peralta Colleges, concludes that a bean holds the same caffeine whatever its roast level, and that by weight dark roast gives more, because its beans are lighter and therefore more numerous. The Seattle Coffee Gear guide says the opposite: by weight, light roasts hold slightly more. With no consensus, we give no figures and advise you not to choose a roast level for its caffeine. As for surface oil, it goes with a deep roast: it rises around second crack.

We have not found any sourced rule linking a roast level to a brewing method or a type of drink, so we will not give you one. What we can say is how to look for yours. If you are starting out, begin in the middle of the scale and move one step each way: it is the fastest way to find your zone. And if you make espresso, remember that yield and grind are set coffee by coffee: our article on dose, yield and time explains the method.

Rather than choosing from the label, compare. Take two coffees from the same origin and process, one lighter and one darker, ideally from the same roaster and roasted on close dates. Brew them with the same method, dose, water and grind, one after the other. Taste hot, then lukewarm: differences show as it cools. Ask yourself three questions. Where do you feel the acidity: at the tip of the tongue, lively, or barely present? Is the bitterness pleasant (like cocoa) or dry? Do you still recognise a fruit, a flower, or only 'roasted'? Write down your answers. Two or three comparisons are enough to know whether you lean light, medium or dark, and what you really look for in a cup. To put the right words on what you taste, our guide to learning to taste coffee gives you the vocabulary.

Roast level is one of the most useful pieces of information to keep next to your score: without it, you cannot understand why one coffee pleases you and another does not. In your notebook, note the level announced by the roaster (light, medium, dark, or their scale), the roast date, the origin, the method and what you taste. After a few weeks a pattern appears: 'I score medium coffees higher', 'dark ones tire me'. You no longer buy at random, you buy what you like. To learn to read the rest of the label, reread our guide to decoding a bag, and to judge a roaster, the one on the signs of a good roaster. Sources consulted: Coffee Review ('Roast Definitions', updated June 2026), Grain d'Expert (March 2026), Seattle Coffee Gear, Roest (roaster's glossary), Sprudge (April 2019). Only facts found in at least two sources are stated; the divergence on caffeine is flagged; verified in October 2026.