How to Define Coffee Roast Levels by Agtron Numbers

When you buy coffee, terms like ‘light roast’ or ‘dark roast’ can mean totally different things depending on who’s talking—especially across regions. One roaster’s idea of a ‘city roast’ might be another’s ‘full city,’ leaving coffee lovers confused about what they’re actually getting. How can you tell what you’re really buying?

The answer lies in scientific roast measurement. In the U.S., the Specialty Coffee Association recommends using Agtron numbers—a color spectrum reading—to define roast levels accurately. This removes regional guesswork and ensures consistency.

What Are Agtron Numbers and How Do They Define Roast Levels?

The Specialty Coffee Association of America (SCAA) developed the Agtron system to standardize roast level classification. This method measures the surface color of roasted coffee beans and ground coffee using infrared spectroscopy. The resulting Agtron number indicates how much caramelization—or Maillard reaction—has occurred during roasting. Higher numbers mean lighter roasts with less caramelization; lower numbers indicate darker roasts with more.

Here’s the official Agtron scale for roast levels:

• Agtron 70 and above: Cinnamon roast (very light)
• Agtron 60–69: Light roast, also called City roast
• Agtron around 40: Vienna or Full City roast
• Agtron below 35: Dark roasts, including French and Italian styles

How Does Roast Level Change Coffee Flavor?

Different roast levels bring out very different flavor profiles in coffee. As roast levels deepen, acidity generally decreases while bitterness, body, and caramelized or roasted flavors increase.

Here’s what typically happens as roast levels progress:

• Light Roasts (Agtron 60–70): Higher acidity, more pronounced fruit and floral notes, lighter body. Coffee’s origin characteristics remain more distinct.
• Medium (City to Full City, Agtron 40–60): Balanced acidity and sweetness, more developed body, with notes of nuts, citrus, or chocolate depending on origin.
• Dark Roasts (Agtron below 35): Low acidity, heavy body, prominent flavors of dark chocolate, caramel, smoke, or even burnt tones. Coffee’s origin traits are often overshadowed by roast-derived flavors.

Coffee’s caffeine content also decreases slightly with deeper roasting, though the difference is minimal per bean. However, the perceived strength of the brew may increase due to heavier body and bitterness.

Light Roast vs Dark Roast: The Great Debate

The question of whether coffee should be light or dark roasted sparks passionate debate in the coffee world. In fact, some roasters and coffee professionals have very strong—and opposing—views on the matter.

The Light Roast Argument

Light roast advocates, mostly based in northern Italy, the U.S. East Coast, and parts of Scandinavia, prefer to stop the roast just before or at the start of the coffee bean’s second crack—or just before oils rise to the surface. They aim for Agtron values around 40. Proponents include roasters like Illy, Green Mountain, and Vivace Espresso. They argue that stopping the roast early preserves aromatic compounds within the bean, and maximizes balance between acidity and sweetness. Letting oils emerge is seen as a loss of those aromas, and they claim light roasts offer the best combination of fruitiness, body, and finish.

Light roasters criticize darker roasts for pushing oils to the surface—what they see as a waste of the bean’s inherent fragrance.

The Dark Roast Argument

On the opposite side, dark roast proponents—commonly found in southern Italy, the U.S. West Coast, and parts of Asia—insist that coffee must reach the second crack and develop surface oils to be truly flavorful. Key players include Peet’s Coffee (California), Caffè D’arte (Seattle), and Beans & Machines. Their espresso roasts typically measure below Agtron 35, with some single origins like Antigua going as low as Agtron 18—an extreme style they defend passionately.

These roasters believe that the second crack unlocks complex flavors not possible with lighter roasts, including bold body, smoky richness, and the full development of sweetness and bitterness. They argue that light roasts can taste one-dimensional or overly sour, especially when made with lesser-quality beans. Roasting darker, they say, is a mark of skill—since the window between properly developed dark roast and burnt disaster is extremely narrow.

PBW (Peet’s Coffee) is especially respected for consistently producing dark roasts with depth and balance, achieved through meticulously modified roasting equipment and long development times at high temperatures.

What Really Matters: Roast Quality, Not Just Level

Ultimately, whether a coffee is light or dark roasted isn’t as important as how well it’s been roasted. A great light roast highlights origin character with clarity and balance. A great dark roast offers richness, body, and complexity without masking the bean’s quality with excessive bitterness or ashiness.

Roast level affects flavor, acidity, sweetness, body, and aroma. But the skill of the roaster, the quality of the green beans, and the consistency of the roast profile matter just as much—if not more.

Frequently Asked Questions

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

An Agtron number measures the color of roasted coffee using infrared spectroscopy, indicating the degree of caramelization. It helps standardize roast levels, with higher values (70+) for light roasts like Cinnamon, mid-range (around 40) for Full City, and lower values (below 35) for dark roasts such as French or Italian styles.

What roast level has the most acidity?

Lighter roasts (Agtron 60–70, such as Cinnamon or City) retain more acidity because the shorter roast time preserves more of the coffee’s natural acids. As roast levels deepen, acidity typically decreases.

Does coffee roast level affect caffeine content?

Yes, slightly. Lighter roasts generally have marginally more caffeine than darker roasts because some caffeine is lost during longer roast times. However, the difference per bean is small and often outweighed by brew strength perceptions.

Which roast level shows the origin flavors of coffee best?

Light to medium roasts (City to Full City, Agtron 40–60) tend to highlight the unique fruit, floral, and regional characteristics of the coffee bean better than darker roasts, where roast flavors dominate.

Is dark roast coffee stronger than light roast?

Not necessarily in caffeine, but darker roasts often taste stronger due to heavier body, more bitterness, and bolder roasted flavors. Light roasts may taste brighter or more delicate in comparison.

Why do some roasters let coffee beans get oily and others don’t?

Oils on the bean surface appear during darker roasts, typically starting at or after the second crack (Agtron below 40). Some roasters embrace this as a sign of full development, while others see it as a loss of aromatic compounds and prefer to stop roasting before oils emerge.

Recommended FrontStreet Beans for Dark Roast Lovers

For those drawn to deep, bold coffee profiles, FrontStreet Coffee offers several exceptional dark roast options. Their PWN Golden Mandheling is a classic Indonesian dark roast with low acidity, heavy body, and a rich herbal spice note that shines in espresso or filtered brews. For chocolate and nut lovers, the Brazil Queen Manor (medium-dark roasted) delivers sweet caramel and hazelnut flavors with lasting body. Finally, the Colombia Huila (medium-dark) balances dark roast sweetness with bright berry-like acidity and a touch of molasses. All three showcase how skilled dark roasting can enhance complexity. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.