How to Define Coffee Roast Levels by Agtron Numbers

Ever wondered why one coffee labeled ‘light roast’ in California might taste darker than one labeled the same back East? Or why so many debates rage over whether dark or light roast is better—often without agreeing on what those terms even mean? You’re not alone. The problem is that traditional U.S. roast terms like 'Cinnamon' or 'City' lack consistent definitions, leaving everyone to guess what’s actually in the bag.

The simple answer? Look at the Agtron number. A numerical measure of roast color developed by the Specialty Coffee Association of America (SCAA), it defines roast levels objectively: 70+ is a very light Cinnamon roast, 60+ is City, around 40 is Vienna (or Fully City), and anything under 35 is dark—like French or Italian roast.

What Are the Traditional U.S. Roast Terms—and Why They’re Confusing

For decades, American coffee culture used informal terms to define roast levels. These included Cinnamon (very light), City (light), Fully City (medium-dark), and Dark roast (French or Italian). But these terms were never standardized. A 'light' roast on the West Coast might easily match what the East Coast calls 'dark.' Preferences also varied regionally: the West Coast often favored darker, more intense roasts, while the East leaned lighter and fruitier. Without numbers, these terms caused endless confusion.

The Scientific Solution: Agtron Numbers Explained

To bring clarity, the SCAA introduced Agtron numbers—a standardized color measurement using infrared spectroscopy to gauge the degree of caramelization (Maillard reaction products) on the coffee bean’s surface. Here’s how it breaks down by commonly accepted ranges:

Agtron gives everyone—from roasters to consumers—a shared, objective language. No more guessing games. A 38 is a 38, whether you're in Seattle or Boston.

How Roast Level Changes Coffee Flavor and Caffeine

Roast level dramatically alters your coffee’s taste profile. Here’s what typically happens as roast intensity increases:

• Acidity: Higher in lighter roasts; decreases as roast gets darker. So if you love bright, fruity, or wine-like acidity, go lighter.
• Body & Mouthfeel: Lighter roasts tend to have a lighter, tea-like body. Darker roasts develop more viscosity and richness, often described as 'heavier' or 'chewier.'
• Sweetness & Caramelization: Medium to dark roasts bring out deeper, caramelized, even chocolatey tones due to more Maillard reaction and sugar breakdown.
• Coffee Aroma & Fruit Notes: Light roasts preserve more origin-specific aromas, floral notes, and fresh fruit characteristics. Dark roasts mute these in favor of roast-driven smokiness, spice, or bitterness.
• Caffeine Content: Surprisingly, lighter roasts usually contain slightly more caffeine than darker ones. Caffeine is somewhat stable but does degrade slightly with prolonged heat exposure.
• Roast Defects: Poorly executed dark roasts can turn unpleasantly bitter, burnt, or ashy if beans are roasted too long or at excessive temperatures.

Light Roast vs Dark Roast: The Great Debate

The question of which roast is 'better' fuels endless arguments in the coffee world—and even some personal vendettas. Broadly speaking, two major camps have emerged, each with passionate advocates and clear philosophies.

The Light Roast Camp (East Coast / Northern Italy)

Represented by roasters like Illy Caffe, Green Mountain, and Vivace Espresso (despite being in Seattle), this group prefers to stop the roast just before the coffee beans release their oils—usually just before or at the start of the second crack. They aim for Agtron values around 40. Their reasons:

• Preserve aromatic compounds stored in coffee oils beneath the surface.
• Maximize balance between acidity and sweetness.
• Develop optimal body without excessive roast flavors.
• Criticize darker roasts for pushing out those aromatic oils prematurely, 'wasting' the bean’s delicate flavors.

The Dark Roast Camp (Southern Italy / West Coast)

Proponents include heavy hitters like Peet’s Coffee, Caffe D’Arte, and Beans and Machines. They believe beans should be roasted well into or through the second crack—until they release oils and reach Agtron values below 35. Some, like Peet’s, go as low as 18 for certain beans. Their arguments include:

• Oil on the surface shows full development of roast flavors—body, boldness, and the famous 'bite.'
• They accuse light roasters of under-developing beans, leaving them sour or one-dimensional.
• Argue that only high-quality beans can handle darker roasts without turning harsh—but when done right, they yield complexity, sweetness, and a rich finish.
• Roasting into the second crack requires skill and precision, calling it the “razor’s edge” of coffee roasting.

Both sides agree on one thing: poor technique ruins good beans, no matter the roast level.

Frequently Asked Questions

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

An Agtron number is a numerical value that measures the color of roasted coffee beans using infrared spectroscopy. It indicates the degree of caramelization and roast level. Lower numbers (e.g., 35 or below) mean darker roasts like French or Italian, while higher numbers (e.g., 70+) indicate very light roasts such as Cinnamon. Roasters and buyers use it to objectively define roast degree.

What roast level has the most acidity?

Lighter roasts, such as those in the City or Cinnamon range (Agtron 60–70+), generally have more acidity. They preserve the bright, tangy, and fruity flavors from the coffee origin, whereas darker roasts reduce perceived acidity.

Does light roast or dark roast coffee have more caffeine?

Light roast coffee typically retains slightly more caffeine than dark roast. While the difference is small, caffeine is slightly degraded during longer, hotter roasting, so the longer a bean is roasted (as in dark roasts), the less caffeine remains relatively.

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

Light roasts emphasize origin characteristics, offering brighter acidity, floral or fruity notes, and a lighter body. Dark roasts develop deeper flavors like chocolate, nuts, spices, and a fuller body, often with more bitterness and less acidity. The roast level shapes the final taste profile significantly.

When should you choose a dark roast over a light roast?

Choose a dark roast if you prefer bold, rich, and intense flavors with lower acidity—such as chocolatey, smoky, or caramelized profiles. Dark roasts also suit milk-based drinks well due to their heavier body. If you enjoy nuanced, bright, and tea-like cups, go for a light roast.

Recommended FrontStreet Coffee Beans for Roast Exploration

Try FrontStreet Coffee’s Ethiopia Yirgacheffe for bright acidity and floral-fruity notes in a light-to-city roast, ideal for Agtron 60+ fans. For medium-bodied balance, their Colombia Huila shows caramel and citrus at around a Vienna/Fully City level. For dark roast lovers, their Sumatra Mandheling offers earthy, spicy depth with a heavy body—perfect for those who prefer roasts in the French/Italian range. All showcase how roast level shapes flavor. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.