Bean knowledge · 5 min

Roast Levels Explained: From Light to Dark

The same green coffee from the same farm becomes a completely different drink at a different roast level. Roast often shapes the impression of a cup more than origin does. And yet "medium" means something different at every roastery, which makes the label confusing.

What roasting does inside the bean

Green coffee is undrinkable as it is. Applying heat changes two things fundamentally. Maillard reactions and caramelization build aromatic compounds, and the structure expands and fractures so the compounds can get out.

As roasting continues, the acids originally present break down while sugars caramelize and bitter, roasty compounds accumulate. Origin character recedes and roast character advances.

At the same time density falls and the structure loosens, so water extracts more easily. That is why dark roasts want lower temperatures: they are already primed to give things up, and heat pushes them past the point quickly.

The levels

The divisions below are widely used, though every roastery draws the lines slightly differently. Treat it as a map rather than a specification.

Visible oil on the surface means medium-dark or beyond. Oil also stales faster, so storage matters more.
Level	Color	Character	Suits
Light	Pale brown	Distinct acidity, origin character intact	Filter, hot water (94–96°C)
Medium-light	Brown	Acidity and sweetness balanced	Filter generally
Medium	Mid brown	Sweetness-led, well balanced	Almost any method
Medium-dark	Deep brown, oil appearing	Fuller body, nutty and rich	Espresso, moka pot
Dark	Near black, oily surface	Bitter and roasty, little acidity	Espresso, cooler water (88–90°C)

Agtron: color as a number

"Medium" points at a different place for every roaster. Agtron numbers exist to remove that ambiguity by measuring color directly.

Light is shone at the bean surface and the reflection measured. Higher numbers mean lighter color, lower numbers mean darker. It is the common language for roast level in specialty coffee.

Few people own an Agtron meter, but knowing the rough mapping helps you interpret what is printed on a bag.

Agtron	Level
75 and above	Light
65–75	Medium-light
55–65	Medium
45–55	Medium-dark
45 and below	Dark

Adjusting the brew to the roast

Using one recipe for every coffee tends to leave light roasts sour and dark roasts bitter. Roast level changes how hard the coffee is to extract, so temperature and grind should move with it.

The principle is simple. Light roasts resist, so brew them harder. Dark roasts give easily, so brew them gently.

Start here when you open a new bag, taste, and move one variable at a time.
Level	Temperature	Grind	Ratio
Light	94–96°C	Slightly finer	1:16 – 1:17
Medium	92–94°C	Standard	1:16
Medium-dark	90–92°C	Standard to coarser	1:15 – 1:16
Dark	88–90°C	Slightly coarser	1:15

Which level should you buy?

There is no correct answer; it depends on how you drink and what you like. A few practical guides do apply.

If you want to taste origin character, light to medium-light is where it lives. The jasmine of an Ethiopian coffee or the grapefruit acidity of a Kenyan disappears as roasting deepens. If you drink with milk or want weight, medium-dark and beyond works better, because it has the intensity to survive dairy.

If you are starting out, start at medium. It is the most forgiving to brew, and working outwards from there is a less frustrating way to find your direction.

Storage varies by level

Deeper roasts have more broken cell structure, so oils migrate to the surface. Surface oil meets oxygen and goes rancid quickly, which means dark roasts have a shorter useful life.

Light roasts hold on somewhat longer because the structure is denser. Either way the rules are the same: airtight, cool, dark.

Recording the roast date and the date you opened the bag builds a picture of which day of a coffee life you liked best. When you buy the same coffee from the same roaster again, that record is immediately useful.