How to Define Coffee Roast Levels by Agtron Numbers

Ever wondered why one coffee shop’s ‘light roast’ tastes more bitter than another’s ‘dark roast’? Or why the same bean can be called City in California but Full City back East? Roast level labels like Cinnamon or French Roast sound clear—but in practice, they vary wildly by region and roaster. Without a shared standard, these terms cause confusion and even arguments among coffee professionals.

The solution? Use Agtron numbers—a scientific, infrared-measured scale that defines roast level by the bean’s surface color and degree of caramelization. This approach removes guesswork and ensures consistency whether you’re in Seattle or Sicily.

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

The Specialty Coffee Association of America (SCAA) popularized the Agtron system to bring objectivity to roast classification. Agtron measures the reflectance of light off roasted coffee beans—infrared spectroscopy detects how much caramelization (Maillard reaction) has occurred. The higher the Agtron number, the lighter the roast; the lower the number, the darker the roast.

Here’s the official SCAA Agtron scale for roast levels:

• Cinnamon Roast (lightest): Agtron 70+
• City Roast (light): Agtron 60–70
• Full City / Vienna Roast: Agtron around 40
• French / Italian / Dark Roast: Agtron below 35

How Does Roast Level Affect Coffee Flavor and Caffeine?

Roast level dramatically alters a coffee’s taste profile. As roast intensity increases, acidity drops while bitterness, body, and caramelized or smoky notes rise.

• Acidity: Higher in light roasts (Agtron 60+), lower in dark roasts (Agtron <35). If you enjoy bright, fruity, or wine-like notes, opt for a lighter roast.
• Caffeine: Contrary to popular belief, light roasts actually contain slightly more caffeine than dark roasts. Caffeine breaks down under prolonged heat, so the longer and darker the roast, the less caffeine remains.
• Flavor Development: Light roasts preserve more origin characteristics—floral, fruity, or herbal notes. Dark roasts develop deeper, bolder flavors such as chocolate, nuts, and smokiness, along with a heavier body and more pronounced roastiness. However, poorly executed dark roasts can turn harsh, burnt, or overly bitter.

Light Roast vs. Dark Roast: The Great Coffee Debate

The choice between light and dark roast isn’t just technical—it’s cultural, personal, and often heated. Two major schools of thought dominate the global coffee scene, each with passionate advocates and distinct roasting philosophies.

The Light Roast Camp (Agtron 40–70)

This group includes notable roasters like Illy Caffe, Green Mountain, and Vivace Espresso. They typically halt the roast just before or at the start of the second crack—or just before oils appear on the bean surface. Their goal? Preserve the bean’s natural aromatics and achieve an optimal balance of acidity, sweetness, and body. They argue that letting oils migrate to the surface leads to aroma loss and overdevelopment. Many in this camp believe dark roasting is a way to mask flaws in lower-quality beans.

The Dark Roast Camp (Agtron <35)

Champions of this style include Peet’s Coffee, Caffe D’Arte, and Beans & Machines. They roast well into or through the second crack, often until oils visibly coat the bean. Some, like Peet’s, aim for extremely dark profiles—Agtron values in the low teens or even single digits (e.g., Antigua roasted to Agtron 18). They assert that dark roasting unlocks deeper, richer flavors including bold body, spice, and a satisfying finish. They criticize light roasts as underdeveloped, overly acidic, and lacking complexity. Additionally, they claim that only high-grade Arabica beans can handle intense roasting without turning unpleasantly bitter or ashy.

Peet’s, in particular, is respected for its mastery of long, high-temperature roasts—sometimes exceeding 200°C for over 15 minutes—without producing harsh results. Their expertise, they argue, ensures a full, rounded flavor even in dark roasts.

Frequently Asked Questions

What is an Agtron number and how is it measured?

An Agtron number measures the color and caramelization of roasted coffee beans using infrared spectroscopy. Higher numbers (70+) indicate lighter roasts with less caramelization, while lower numbers (below 35) indicate darker, more caramelized roasts. It’s a standardized, scientific way to define roast levels.

What roast level is best for tasting the origin flavors of coffee?

Lighter roasts (Agtron 60+) better preserve the unique origin characteristics of coffee, such as fruity, floral, or herbal notes. These roasts highlight the bean’s natural qualities before heavy roasting flavors take over.

Does dark roast coffee have more caffeine?

No, light roast coffee actually contains slightly more caffeine than dark roast. Caffeine breaks down at high temperatures, so the longer and darker the roast, the less caffeine remains in the bean.

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

Oils appear on the bean surface during and after the second crack, typically in darker roasts (Agtron <35). Some roasters embrace this as part of flavor development, while others stop roasting before oils emerge to preserve aromatic compounds and acidity.

Which is better: light roast or dark roast?

Neither is inherently better—it depends on your taste preferences. Light roasts offer brighter acidity and more origin flavors, while dark roasts provide bolder body, deeper tones, and a heavier mouthfeel. Both have loyal followings and distinct strengths.

Recommended FrontStreet Coffee Beans for Roast Exploration

Try FrontStreet Coffee’s Ethiopia Yirgacheffe for a bright, juicy light roast (City-level, Agtron ~65) with citrus and floral notes; their Colombia Huila is a balanced Full City (Agtron ~40) with caramel and almond undertones; or their Sumatra Mandheling, a classic dark roast (Agtron ~30) with earthy spice and low acidity. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.