Roast Level Comparator

Side-by-side comparison of roast levels from light to dark. Visualize how roasting temperature affects flavor, acidity, body, and caffeine content. Includes Agtron scale reference and recommended brew methods for each level.

Calculator

Roast A

Roast B

Key Differences

How to Use

1
Select two roast profiles to compare
Choose any two roast levels (light, medium-light, medium, medium-dark, dark, or espresso roast) to compare side by side. The comparator maps the physical, chemical, and flavor changes that occur between the two levels along the roast development curve.
2
Review the flavor and chemistry differences
Examine how each roast level affects acidity, body, sweetness, and bitterness based on Maillard reaction and pyrolysis progression. Use the SCA color scale (Agtron score) reference to understand where each roast sits on the standardized 0-100 light-to-dark spectrum.
3
Match your brewing method to the roast
Apply the brewing parameter adjustments the comparator recommends for each roast level. Dark roasts typically benefit from lower brew temperatures (88-92°C) and coarser grinds; light roasts often need higher temperatures (93-96°C) and finer grinds to achieve balanced extraction.

About

The Roast Comparator maps the transformation that coffee undergoes from green bean to the roasted product in your grinder, showing how roast level determines the flavor, chemistry, and brewing behavior of any given bean. Roasting is fundamentally a process of controlled transformation — applying heat to drive the Maillard reaction and pyrolysis reactions that create coffee's characteristic flavors while preserving or eliminating origin characteristics based on how far the roast develops.

The SCA's Agtron scale provides an objective framework for roast level comparison, translating the continuous spectrum of roast development into standardized reference points. Light roasts (Agtron 60-85) preserve the most origin characteristics — the terroir, variety, and processing-driven aromatics that make Ethiopian coffee taste distinctly Ethiopian. Dark roasts (Agtron 25-45) replace origin character with roast-derived flavors of chocolate, tobacco, and carbon that are more uniform across origins. Neither extreme is inherently superior; they serve different brewing contexts, palate preferences, and applications.

Understanding roast level is also the key to adjusting your brewing parameters correctly. The physical changes that occur during roasting — increased porosity, decreased density, changed solubility — require different extraction approaches. Light roasts need more aggressive extraction conditions (higher temperature, finer grind, longer contact time) because their intact cell structure and lower solubility resist extraction. Dark roasts extract rapidly and can easily become bitter with excessive extraction. The comparator gives you the framework to approach each roast level with appropriate parameters rather than applying one-size-fits-all brewing rules.

FAQ

What happens chemically during coffee roasting?

Coffee roasting is driven by two major chemical processes: the Maillard reaction and pyrolysis (caramelization and beyond). The Maillard reaction begins around 150°C, combining amino acids with reducing sugars to create hundreds of new aromatic compounds responsible for bread-like, caramel, and nutty flavors — the same process that browns bread and seared meat. Around 170°C, sugar pyrolysis begins, producing caramel notes. As temperature increases past 200°C, pyrolysis of longer-chain compounds creates darker, more bitter roast-forward flavors — chocolate, tobacco, carbon. The first crack (around 196°C) is the point where steam and CO2 pressure cause the bean to expand and crack audibly. Light roasts are stopped before or just after first crack; dark roasts continue through second crack.

What is the Agtron scale and why does it matter?

The Agtron scale is a standardized spectrophotometric measurement system used to objectively quantify coffee roast level. Agtron instruments measure the reflectance of ground or whole coffee under near-infrared light, producing a score from 0 (darkest/most roasted) to 100 (lightest/least roasted). Specialty coffee's SCA uses the Agtron scale to establish reproducible roast level standards that enable consistent communication between roasters, buyers, and quality evaluators. Without an objective scale, 'medium roast' is entirely subjective — one roaster's medium is another's dark. The Agtron scale allows roasters to specify 'Medium Roast — Agtron 55' and have that mean the same thing to anyone with access to the measurement tool. Many specialty cafes publish Agtron scores on their coffee descriptions.

Does dark roast actually have more caffeine?

No — this is one of coffee's most persistent misconceptions. Caffeine is a thermally stable alkaloid that does not degrade significantly during roasting. The confusion arises from how coffee is measured. When you measure by volume (scoops), dark roast appears to have less caffeine because the expanded, less dense dark roast beans pack less tightly, so you get less coffee mass per scoop and therefore less caffeine. When measured by weight (grams on a scale), Arabica light and dark roasts contain essentially the same caffeine per gram. If anything, very dark roasts have slightly less caffeine per gram because mass loss during roasting (water, CO2, volatile compounds) slightly concentrates the caffeine percentage while also reducing total bean mass — effects that roughly cancel out.

How does roast level affect acidity?

Coffee's perceived acidity decreases with increasing roast level through chemical transformation rather than simple dilution. Green coffee contains significant levels of chlorogenic acids (CGAs) — powerful antioxidants comprising 6-9% of green bean mass. During roasting, CGAs progressively degrade into quinic acid, caffeic acid, and other breakdown products. Quinic acid has a harsh, astringent perceived acidity quite different from the bright, clean citric and malic acids preserved in light roasts. Light roasts preserve more intact CGAs and fruit-derived organic acids (citric, malic, tartaric), producing bright, clean acidity associated with fruit notes. Dark roasts have lower total acidity but what remains is perceived as harsher, less pleasant, and more phenolic in character.

What roast level is best for espresso?

Espresso's high-pressure, short-extraction format is forgiving of certain roast characteristics and particularly suited to medium to medium-dark roasts, though this is a strong historical convention rather than a physical necessity. Darker roasts have more soluble surface compounds that extract quickly under 9-bar pressure, producing consistent results in the 25-30 second window. They also have lower perceived acidity, which is desirable in milk-based drinks where bright acidity can clash with dairy sweetness. The third-wave specialty movement has demonstrated that well-developed light roasts can produce exceptional espresso with more complex, fruit-forward profiles — but they require more precise grind adjustment, temperature control, and extraction technique to avoid sourness. Most contemporary specialty cafes now offer both traditional medium-dark and lighter specialty espresso roasts.