Roast color is the first thing you notice about a bag of coffee, and for most of the industry's history it was one of the hardest things to describe precisely. Roasters reached for words like "medium," "full city," or "French," but each of those terms meant something slightly different in every roastery, and none of them could be written on a spec sheet a supplier and a buyer would read the same way. The Agtron scale changed that by turning roast color into a number that any two people can compare.
Today, when a roaster says a coffee is "a 58 whole bean, 72 ground," they are speaking a shared, near-universal language of roast degree. This guide explains what that number is, how the machine reads it, how it maps onto the Specialty Coffee Association's roast color tiles, and the one thing it cannot tell you: how the coffee will actually taste. Color is a powerful standard, but it measures the degree of roast, not the development behind it.
What "Agtron" means and how the reading works
Agtron is a brand of near-infrared spectrophotometer, made by a company of the same name, that has become so dominant in coffee that "Agtron number" is now common shorthand for roast color regardless of which instrument produced it. The device shines light onto a sample of roasted coffee and measures how much of that light is reflected back. Darker coffee absorbs more and reflects less, returning a lower number; lighter coffee reflects more and returns a higher one.
The reason near-infrared light is used rather than the naked eye is precision and repeatability. Agtron's coffee analyzers work in the near-infrared band, where reflectance tracks closely with the chemical changes of roasting — particularly the browning and caramelization of sugars at and near the bean surface. The result is a reading that is far more consistent than a visual judgment, which shifts with lighting, screen calibration, and the individual eye. This is the core appeal of color measurement over subjective naming: two operators on two continents can arrive at nearly the same figure. For the wider context of what happens inside the roaster, see our overview of what coffee roasting is.
Reading the Agtron scale from light to dark
The number most roasters quote comes from the Agtron "Gourmet" scale, the version the SCA adopted for specialty coffee. On this scale, higher numbers mean lighter roasts and lower numbers mean darker roasts. The range is commonly described as running from roughly 95 at the very light end down to about 25 at the very dark end, though these anchors are best treated as conventional reference points rather than hard physical limits — different sources and different sample preparations will shift them slightly.
It is worth knowing that Agtron machines can also report on a separate "Commercial" scale, whose values differ from the Gourmet numbers, so a bare figure is only meaningful once you know which scale it came from. In practice, most specialty roasters quote Gourmet numbers, and many operate their whole-bean readings somewhere in the broad middle of the range depending on the profile they are chasing — lighter for delicate, acidity-forward coffees and darker for bittersweet, roast-driven ones. If you want the sensory picture behind those extremes, our guides to coffee roast levels and light roast versus dark roast cover how flavor shifts across the spectrum.
The SCA Roast Color Classification and color tiles
The Specialty Coffee Association's Roast Color Classification system is built directly on this measurement. It pairs Agtron Gourmet numbers with a set of physical color tiles — commonly a set of eight — that step down the scale in roughly ten-point intervals, from about 95 at the lightest to about 25 at the darkest. Each tile carries a descriptive label, and while the exact names have varied over the years, they typically run along the lines of:
| Approx. Agtron (Gourmet) | Common SCA label | General character |
|---|---|---|
| ~95 | Very Light | Grassy, high acidity, thin body |
| ~85 | Light | Bright, origin-forward |
| ~75 | Moderately Light | Sweet, acidity still prominent |
| ~65 | Light Medium | Balanced, rounded |
| ~55 | Medium | Fuller body, gentler acidity |
| ~45 | Moderately Dark | Roast tones emerging, bittersweet |
| ~35 | Dark | Roast-dominant, low acidity |
| ~25 | Very Dark | Smoky, bitter, oily surface |
These tiles let a roaster hold a sample beside a physical reference and place it on the scale even without a machine on hand, and they give buyers, competition judges, and quality control labs a shared vocabulary. The labels above should be read as approximate; the value of the system is the number underneath them, which is what makes the classification consistent from one lab to the next.
Whole beans versus ground: the gap that reveals evenness
An Agtron reading can be taken two ways: on whole roasted beans and on the same coffee ground. These two numbers are almost never identical, and the difference is diagnostic. Ground coffee usually reads lighter — a higher number — than whole beans from the same batch. Grinding exposes the bean's interior, which has typically taken on less color than the exposed outer surface, and the fine, densely packed ground sample also scatters and reflects light more uniformly.
The size of that gap — sometimes called the roast delta — is a clue to how evenly the coffee roasted. A small gap suggests the outside and the inside of the bean reached a similar degree of roast, which points to even, well-managed heat transfer. A large gap suggests the surface ran ahead of the core, a pattern often linked to scorching, tipping, or a roast that moved too fast for heat to penetrate. Roasters watch this relationship as a quality signal, and it connects to what happens right around first crack and how heat is applied through the rate of rise. On its own, a single whole-bean number tells you where a roast landed; the whole-bean-versus-ground pair tells you a little about how it got there.
Why measuring color standardizes coffee
The practical payoff of the Agtron system is communication and consistency. Because the number is objective and repeatable, a roaster can specify a target for a blend, a green buyer can confirm a sample matches a previous shipment, and a competition can classify entries on the same footing. It removes the ambiguity of words like "medium," which mean different things in different places, and replaces them with a figure that travels.
Inside a roastery, color measurement is above all a consistency tool. By checking each batch against a target number, a roaster can catch drift — a batch that came out a few points darker than the last — and correct the profile before it ships. That is why quality control programs, from small operations to large ones, log Agtron readings alongside time and temperature data. For the people whose job is to evaluate coffee formally, such as an SCA Q grader, a documented roast color is part of preparing samples fairly, since roast degree itself influences how a coffee shows up on the cupping table.
The limitation: color is degree of roast, not development
Here is the single most important caveat, and the reason color measurement is a starting point rather than a verdict: the Agtron number reports the degree of roast — how far the browning reactions progressed — but it says nothing about development, meaning how evenly and completely the flavor-forming reactions ran throughout the bean over the course of the roast. Two coffees can land on exactly the same Agtron number and taste dramatically different.
A coffee rushed to a given color in a short, hot roast can arrive under-developed, tasting grassy, sour, or vegetal despite looking "medium." Another coffee taken to the same color over a longer, gentler curve can taste sweet, balanced, and complete. The color is the same; the eating experience is not. This is why measurement and tasting are complementary rather than interchangeable — the machine anchors the color, and cupping reveals whether the roast behind that color actually delivered. To go deeper on the reactions the number cannot see, read our guide to coffee roast development. Treat the Agtron figure as a reliable label for degree of roast, and never as a promise about flavor.
Frequently asked questions
What is a good Agtron number for coffee?
There is no single "good" number — it depends entirely on the coffee and the style you want. Higher numbers are lighter and lower numbers are darker, and specialty roasters commonly work somewhere in the broad middle of the Gourmet scale on whole beans. The right target is the one that suits the bean and produces the flavor you are after, verified by tasting rather than by the number alone.
Does a higher Agtron number mean a lighter or darker roast?
A higher Agtron number means a lighter roast. Lighter coffee reflects more of the near-infrared light the instrument shines on it, so it returns a higher value, while darker coffee absorbs more light and returns a lower one. On the Gourmet scale this runs roughly from about 95 at the very light end down to about 25 at the very dark end.
Why does ground coffee read a lighter Agtron number than whole beans?
Grinding exposes the bean's interior, which usually took on less color than the outer surface, and the fine, evenly packed ground sample also reflects light more uniformly. Both effects push the ground reading lighter, or higher. The gap between the whole-bean and ground numbers is used as a rough marker of how evenly the coffee roasted.
Is Agtron the same as the SCA roast classification?
They are closely linked but not identical. Agtron is the instrument brand and the color scale; the SCA Roast Color Classification is a system of labeled color tiles built on top of Agtron Gourmet numbers. In other words, the SCA classification uses the Agtron measurement as its underlying reference, so the two are usually quoted together.
Can two coffees have the same Agtron number but taste different?
Yes, and this is the key limitation of color measurement. The Agtron number captures the degree of roast — how dark the coffee is — but not its development, meaning how thoroughly the flavor-forming reactions ran. A coffee rushed to a color can taste under-developed and sour, while one taken to the same color more gently can taste sweet and balanced.