How to Define Coffee Roast Levels by Agtron Numbers

Ever wonder why your ‘light roast’ cup from a Seattle café tastes deeper than the one you had in Boston? Or why two bags labeled ‘medium’ can differ wildly in acidity and bitterness? The truth is, traditional roast terms like ‘Cinnamon,’ ‘City,’ or ‘French’ are vague and inconsistent—especially across regions. Without a shared standard, one roaster’s ‘light’ might be another’s ‘medium.’

Here’s the clear answer: US specialty coffee pros now rely on Agtron numbers—a scientific measurement of surface lightness using infrared spectroscopy. A roast scored 70+ is a very light Cinnamon roast; 60–69 is a classic City (light); around 40 hits Fully City (Vienna-style medium-dark); and anything below 35 is a dark or French/Italian-style roast.

Why Roast Level Terms Used to Be Confusing

For decades, American coffee culture used informal labels to describe roast degree: Cinnamon (the lightest), City (light), Fully City (medium-dark), and Dark roast (including Italian and French styles). But these terms were never standardized. Regional taste preferences played a huge role—West Coast roasters often roasted darker than their East Coast counterparts. As a result, a ‘light’ roast in California might taste closer to a ‘medium’ or even ‘dark’ in New York. These terms created more confusion than clarity.

The Science Behind Agtron Roast Measurement

To solve the inconsistency, the Specialty Coffee Association of America (SCAA) championed the use of Agtron numbers. This system measures the roast level based on the coffee bean’s surface color and caramelization via infrared readings. The key scale is as follows:

• Agtron 70 and above: Very light roast (Cinnamon)
• Agtron 60–69: Light roast (City)
• Agtron around 40: Medium-dark or Vienna/Fully City
• Agtron below 35: Dark roast (French, Italian, and espresso roasts)

This numerical approach removes subjectivity. By using actual data, roasters and consumers can now understand exactly how light or dark a coffee is roasted—no more guessing games.

How Roast Level Affects Coffee Flavor

Roast level dramatically influences a coffee’s taste profile. Here’s how:

• Acidity: Higher acidity (bright, fruity, tart notes) is found in lighter roasts. As roast intensity increases, acidity decreases.
• Coffee Body & Mouthfeel: Light roasts tend to have a lighter, tea-like body, while darker roasts develop more richness, heaviness, and sweetness (often described as ‘body’).
• Coffee Aroma & Fragrance: Fruity, floral, and sugary aromas are more pronounced in lighter roasts. As the roast darkens, these fade, making way for deeper, roasted, caramelized, or even smoky notes.
• Caffeine Content: Contrary to popular belief, lighter roasts actually retain slightly more caffeine than darker ones—because some caffeine is lost during extended roasting.
• Flavor Development: Light roasts preserve origin characteristics like fruit, floral, and herbal notes but may lack the deeper complexity of darker roasts. Dark roasts bring out flavors like chocolate, nuts, caramel, and bold bitterness—but if over-roasted, can turn harsh, burnt, or ashy.

The Great Light vs. Dark Roast Debate

The question of ideal roast level sparks passionate debate in the coffee world. On one side are proponents of lighter roasts—mostly based in Northern Italy and the US East Coast. They aim for Agtron values around 40, stopping the roast just before or as the first signs of coffee oils appear on the bean surface (just before the start of the second crack). Notable advocates include Illy Caffe, Green Mountain, and Vivace Espresso. Their philosophy is that coffee oils hold essential aromatic compounds, and preserving them enhances balance between brightness and body. They argue that letting oils emerge leads to unnecessary aroma loss and a less nuanced cup.

On the flip side are the dark roast advocates, mainly from Southern Italy and the US West Coast. Roasters like Peet’s Coffee (San Francisco), Caffe D’Arte (Seattle), and Beans and Machines prefer beans roasted well into or past the second crack—until oils rise to the bean’s surface. Their dark roasts often measure below Agtron 35, with some single origins (like Antigua) reaching extreme levels like Agtron 18. They argue that this level of roast fully develops the coffee’s bold, bitter-sweet complexity, including notes of spice, dark chocolate, and smokiness. They criticize lighter roasts as underdeveloped or overly acidic and suggest that the preference for light roasts may also stem from cost-saving measures, since only high-quality beans can handle intense roasting without turning unpleasantly bitter.

Peet’s, in particular, is respected for mastering long, high-temperature roasts (over 200°C for 15+ minutes) that avoid excessive bitterness while achieving deep, rich flavor. Their success is partly attributed to custom modifications of roasting equipment to manage these extreme profiles.

Frequently Asked Questions

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

An Agtron number is a scientific measurement of a coffee bean’s roast level based on its surface color and caramelization, determined using infrared spectroscopy. Roasters and industry professionals use it to objectively classify roast degree: 70+ is very light (Cinnamon), 60–69 is light (City), around 40 is medium-dark (Fully City/Vienna), and below 35 is dark (French/Italian).

Does roast level affect coffee acidity?

Yes. Lighter roasts generally have higher acidity, offering brighter, fruitier, and more tart flavors. As the roast gets darker, acidity diminishes, resulting in a smoother, often more bitter or chocolatey cup.

Which roast level has more caffeine?

Lighter roasts retain slightly more caffeine than darker roasts. Although the difference is small, caffeine content decreases marginally during prolonged roasting, meaning a very dark roast will have marginally less caffeine than a very light one.

What are the flavor differences between light and dark roasts?

Light roasts highlight origin characteristics like fruit, flowers, and acidity, with a lighter body. Dark roasts develop deeper flavors such as chocolate, nuts, caramel, and smokiness, with more body and bitterness. However, poorly executed dark roasts can taste burnt or overly harsh.

Why do some coffee regions prefer lighter roasts and others darker?

Regional taste preferences drive roast style. The US East Coast and Northern Italy often favor lighter roasts to preserve acidity and origin notes, while the US West Coast and Southern Italy lean toward darker roasts for bold, rich, and bitter-sweet profiles.

Is there a perfect roast level for all coffee beans?

No. The ideal roast level depends on the bean’s origin, processing method, and desired flavor profile. Some beans shine when lightly roasted to highlight acidity and fruit, while others benefit from darker roasting to develop body and complexity.

Recommended FrontStreet Beans for Dark Roast Lovers

For those drawn to darker roast profiles, try FrontStreet Coffee’s PWN Golden Mandheling, known for its low acidity, bold body, and spicy herbal depth. The Colombia Huila is roasted medium-dark to enhance black chocolate and caramel notes with a structured mouthfeel. For balanced nuttiness and cocoa, the Brazil Queen Manor offers smooth sweetness and lingering maltiness. All three showcase the rich potential of darker roasts. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.