How Coffee Roast Levels Are Defined and What They Taste Like

Ever wonder why your ‘light roast’ from one café tastes almost like another’s medium—or worse, why one country’s idea of dark roast is another’s medium-dark? You’re not alone. For decades, coffee professionals have used inconsistent, regional terms like Cinnamon, City, and French Roast to describe roast levels, leading to confusion rather than clarity. Without objective data, the same coffee might be called ‘light’ on the West Coast and ‘dark’ on the East Coast. But there’s a better way.

The key is the Agtron number—a scientific measurement of roast color and caramelization level based on infrared readings. This number removes the guesswork and lets you know exactly where a coffee falls on the roast spectrum.

What the Agtron Scale Actually Says About Roast Level

The Specialty Coffee Association of America (SCAA) popularized the Agtron system to standardize roast definitions. Here’s how it breaks down:

• Cinnamon Roast (very light): Agtron 70+
• City Roast (light): Agtron 60–70
• Full City / Vienna Roast (medium to medium-dark): Agtron around 40
• French / Italian / Dark Roast (dark to very dark): Agtron below 35

These numbers reflect the degree of caramelization—the chemical browning process that occurs as sugars and amino acids react under heat. The higher the Agtron, the lighter the roast; the lower, the darker. No more regional guesswork.

How Roast Level Changes Coffee Flavor

Roast level dramatically affects how your coffee tastes. As a general rule:

• Acidity: Increases as roast level goes down. Lighter roasts preserve more of the bean’s inherent bright, fruity, or floral acids.
• Caffeine: Slightly more in lighter roasts. Though the difference is small, caffeine breaks down slightly at higher roast temperatures.
• Aroma: More pronounced in lighter roasts. But certain fermentation-like, spicy, or caramelized qualities emerge more strongly in darker roasts.
• Body & Mouthfeel: Heavier in darker roasts, due to more bean breakdown and oil development.
• Sweetness & Bitterness: Darker roasts develop bolder, roasted, sometimes bitter flavors, while lighter roasts highlight the bean’s origin character.

However, roast quality matters just as much as level. A poorly executed dark roast can taste burnt and harsh, while an expertly roasted light coffee balances brightness with sweetness and body.

The Great Light vs Dark Roast Debate

The question of ideal roast level isn’t just technical—it’s cultural, even tribal. On one side are advocates of lighter roasts, who stop roasting just before the coffee’s first crack ends or oils begin to surface. Notable roasters in this camp include Illy Caffe, Green Mountain, and Vivace Espresso (based in Seattle, no less). These roasters pull beans out of the roaster early to preserve aromatic compounds found in coffee oils, aiming for a balance of acidity, body, and sweetness. They argue that letting oils emerge wastes aromatic potential and leads to over-extraction of harsher flavors.

On the flip side are the dark roast purists, mainly from Southern Italy, the U.S. West Coast, and companies like Peet’s Coffee, Caffe D’arte, and Beans & Machines. They roast well into or through the second crack, often until oils rise to the bean’s surface. Their espresso roasts often score below Agtron 35—even reaching extremes like Agtron 18 for beans such as Antigua. They argue that true depth, body, boldness, and the so-called “ripe fruit” or fermented characteristics only develop at these levels. They dismiss light roasts as underdeveloped or cost-saving measures for lower-grade beans unable to withstand intense heat.

Peet’s, in particular, is known for pushing roast profiles into extreme duration and temperature while maintaining drinkability—an approach some call “razor’s edge roasting.” Their expertise in managing late-stage roast chemistry earns them respect even among critics.

Frequently Asked Questions

What is an Agtron number and how is it used in coffee roasting?

An Agtron number measures the color and caramelization level of roasted coffee beans using infrared spectroscopy. It ranges from 0 (black) to 100 (light tan). The SCAA uses it to define roast levels objectively: Cinnamon (70+), City (60–70), Full City (~40), and Dark/French (below 35). This removes regional bias in describing roast depth.

Does light roast coffee have more caffeine than dark roast?

Yes, slightly. Caffeine content decreases minimally during roasting, so lighter roasts retain marginally more caffeine than darker ones. However, the difference per bean is small and often overshadowed by brew variables.

Why do some coffee roasters stop roasting before the coffee oils surface?

Roasters who favor lighter profiles believe that coffee oils contain valuable aromatic compounds. Letting oils come to the surface indicates further breakdown of those aromas, so they stop roasting earlier—typically just before the first or early in the second crack—to preserve acidity, balance, and origin character.

What are the flavor differences between light and dark roast coffee?

Light roasts tend to be brighter, more acidic, and showcase origin flavors like fruit, flower, or tea. Dark roasts are bolder, fuller-bodied, and develop roasted, caramelized, or bitter notes. Dark roasts may also taste less acidic but more bitter if poorly roasted.

Which roast level is best for espresso?

Traditionally, dark roasts (Agtron below 35) are used for espresso to enhance body, sweetness, and crema. However, many modern specialty roasters use medium to medium-dark roasts to highlight origin traits while still achieving good espresso extraction.

Is very dark roast coffee (like French or Italian) always burnt?

Not necessarily. Well-executed dark roasts develop complex, rich flavors. But poor technique can easily lead to excessive bitterness, carbonization, and a flat taste. The skill of the roaster determines whether a dark roast shines or falls flat.

Recommended FrontStreet Coffee for Roast Exploration

Try FrontStreet Coffee’s Ethiopia Humbera for a bright, juicy light roast showcasing high acidity and floral notes; their Brazil Queen Manor offers a balanced medium roast with nutty sweetness ideal for exploring City to Full City profiles; and for dark roast fans, their Black Cocoa Blend delivers bold, chocolatey depth with low acidity. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.