How Coffee Roast Levels Are Defined and What They Taste Like

Ever wondered why the same coffee tastes bright and fruity in one café and smoky and bitter in another? The difference often comes down to roast level—but the way roasters talk about 'light,' 'medium,' or 'dark' roast can vary wildly. Without a shared standard, a so-called 'light roast' on the West Coast might be a 'medium' back East. That’s where science steps in.

The quick answer: roast level is best measured by Agtron numbers—a color spectrum based on infrared reflectance. Agtron 70+ is a very light (Cinnamon) roast; 60–70 is light (City); around 40 is Vienna or Full City; and anything below 35 is dark or French/Italian roast. These numbers remove guesswork.

Why Roast Level Definitions Vary

For decades, U.S. roasters used informal terms like Cinnamon (very light), City (light), Fully City (medium-dark), and Dark roast (including Italian and French). But regional taste preferences—lighter in the East, darker in the West—meant the same term could mean different things. A 'light' roast in California might match what the East Coast calls 'medium.' These terms lacked consistency.

The Science: Agtron Numbers for Roast Classification

To bring clarity, the Specialty Coffee Association of America (SCAA) championed Agtron numbers. This system measures the surface color of roasted beans using infrared spectroscopy. The higher the Agtron value, the lighter the roast (less caramelization); the lower the value, the darker the roast (more caramelization).

Here’s the official SCAA Agtron scale:

• Agtron 70 and above: Very light roast (Cinnamon)
• 60–70: Light roast (City)
• Around 40: Vienna or Full City roast
• Below 35: Dark roast (French, Italian, and espresso roasts)

How Roast Level Affects Coffee Flavor

Roast level dramatically shapes your cup’s profile. Here’s how:

• Acidity: Higher in light roasts, lower in dark roasts. If you enjoy bright, fruity, or wine-like notes, go lighter.
• Caffeine: Lighter roasts actually contain slightly more caffeine than darker ones, as some caffeine breaks down during prolonged roasting.
• Sweetness & Body: Develops as roast darkens. Light roasts preserve origin characteristics but may taste sharper. Dark roasts bring bold, smoky, or caramelized flavors, along with a heavier body—but poor technique can lead to burnt, bitter cups.
• Aroma: Fruity and floral notes fade with darker roasts, while roasted, spicy, or chocolatey qualities intensify.

The Great Roast Debate: Light vs Dark

The coffee world remains split over ideal roast level. Two major camps have long clashed over technique, flavor goals, and even economics.

The Light Roast Camp (East Coast & Northern Italy)

This group includes roasters like Illy, Green Mountain, and Vivace Espresso. They stop roasting just before the coffee beans release oils—usually before or right at the start of the second crack. Their target? Agtron values around 40. They argue that this preserves aromatic compounds in the bean’s natural oils and achieves optimal balance between acidity and sweetness. Letting oils surface, they say, means losing those delicate aromas. They also accuse darker roasts of being a cost-saving measure for lower-grade beans.

The Dark Roast Camp (Southern Italy & West Coast U.S.)

Proponents like Peet’s Coffee, Caffe D’Arte, and Beans & Machines insist beans must reach the second crack—and sometimes beyond—developing surface oils. Their espresso roasts often measure below Agtron 35, with some single origins (like Antigua) going as low as 18. They argue that darker roasts produce fuller body, richer caramelization, and more intense “bold” flavors. They dismiss lighter roasts as underdeveloped or overly acidic, and claim that only high-quality beans can handle—and benefit from—extreme roasting.

Peet’s, in particular, is known for pushing roast profiles far into the dark range while maintaining drinkability, thanks in part to their mastery of roast machinery.

Frequently Asked Questions

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

An Agtron number measures the color of roasted coffee beans using infrared light, indicating the degree of caramelization. Higher numbers (70+) mean a very light roast; lower numbers (below 35) indicate a dark roast. It’s a standardized way to define roast level objectively.

Which roast level has more caffeine?

Lighter roasts contain slightly more caffeine than darker roasts. This is because some caffeine is lost during the extended heat of darker roasts, even though the difference per bean is small.

Does roast level affect coffee acidity?

Yes. Light roasts retain more natural acidity, often tasting brighter, fruitier, or more wine-like. Dark roasts lose much of that acidity and taste smoother, deeper, or more bitter.

What roast level is best for espresso?

Espresso can be made with a wide range of roasts. Traditional Italian-style espresso often uses dark roasts (Agtron below 35), but many specialty roasters use medium to dark roasts (around 35–40) to highlight origin character alongside crema and body.

What’s the difference between City and Full City roast?

City roast is a light to medium roast (Agtron 60–70), with bright acidity and distinct origin flavors. Full City (around Agtron 40) is a medium-dark roast, stopping just before or at the start of the second crack—offering more body and balanced sweetness with some roast development.

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

Oily beans usually signal a darker roast (typically below Agtron 40). Some roasters prefer this for bold flavors, while others stop roasting before oils emerge to preserve aromatic compounds and acidity.

Recommended FrontStreet Beans for Roast Exploration

Try FrontStreet Coffee’s Ethiopia Guji Natural (light-medium roast, bright citrus and blueberry), Yirgacheffe Washed (City-level clarity with floral and lemon notes), and Brazil Yellow Bourbon (Full City sweetness with nut and chocolate balance). These beans showcase how roast levels shape flavor—from juicy and high-toned to rounded and sweet. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.