The Agtron scale is the number system coffee roasters use to describe roast color. A color reader shines near-infrared light onto a coffee sample and measures how much of it bounces back. Lower numbers mean darker coffee. Higher numbers mean lighter coffee.
That one number lets a roaster in Portland and a buyer in Nairobi talk about the same roast without arguing over what "medium" means. This guide explains where Agtron numbers come from and why there are two Agtron scales. It also covers why roasters list two readings per coffee, and how to turn a reading into a roast target you can hit batch after batch. Shopping for the instrument itself? CoffeeTec's roast color analyzers collection lists new and used readers from Agtron, Lighttells, Javalytics and others.
An Agtron number is a reflectance reading, not a picture of color. The instrument reads a narrow band of near-infrared light that sits outside what your eye can see. That band tracks the browning of sugars during the roast, so the number follows roast chemistry more closely than visible color does.
Here's the practical upshot. Two batches can look identical on the cooling tray and still read several points apart. The reader catches differences your eye misses.
Agtron Inc. is the Nevada company that built the original roast color analyzers. Its name stuck, so roasters say "Agtron number" even when the reading comes from another brand's meter.
Every reader follows roughly the same routine. The details change by model, but the sequence below covers the Agtron M-Basic series, the E20-CP and most benchtop units from other makers.
Calibration is what makes the number trustworthy. Agtron readers use reference disks to set the scale's span. The E20-CP runs a two-point calibration. That holds the scale steadier over time than the single-point method on the older E10-CP. If a used reader arrives without its reference disks, treat its numbers as relative until it's recalibrated.
Sample prep moves the number too. A finer grind reads lighter. A loosely packed dish reads differently from a firmly packed one. Pick one grind setting and one fill method, write them down, and never change them mid-season.
The Gourmet scale gives the same coffee a higher number across a wider range, and the Commercial scale uses a narrower band. That difference is where most confusion starts.
| Feature | Gourmet scale | Commercial scale |
|---|---|---|
| Typical instruments | Agtron M-Basic, M-Basic II and M-Basic III | Agtron E-series (E10-CP, E20-CP); the E20-CP can be calibrated to either scale |
| Number range | Wider; very light samples read well above 100 | Narrower band |
| Same coffee reads | A higher number | A lower number |
| Who uses it most | Specialty roasters, coffee reviewers and the SCA roast color tiles | High-volume production plants and older roast specs |
Our advice is simple. Always write the scale next to the number. "58 Gourmet ground" is a spec. "58" on its own is a guess, because a Commercial-scale 58 is a much lighter coffee than a Gourmet-scale 58.
A roasted bean is darker on the outside than in the center. The surface takes the most heat. Read the whole beans and you measure that darker shell. Grind them and you mix in the lighter interior, so the ground reading comes out higher.
That's why you'll often see two numbers written with a slash. Coffee Review lists every coffee this way on the Gourmet scale, whole bean first and ground second. A 55/68 coffee read 55 as beans and 68 once ground. It then averages the pair to assign a roast name.
The gap between the two numbers is the part many roasters skip, and it's often the more useful reading.
Track both numbers and the gap in your roast log. The ground number tells you where you landed. The gap tells you how you got there.
The Agtron and SCA roast color classification system uses eight reference tiles, numbered in steps of ten. Roasters compare a ground sample against the tiles, or read it on a meter and match the number. The chart below uses those tile numbers on the Gourmet scale for ground coffee.
| SCA tile (Agtron number) | Roast name | What you'll usually see |
|---|---|---|
| #95 | Very Light | Tan grounds, dry bean surface, grain or tea-like notes if underdeveloped |
| #85 | Light | Light cinnamon color, high acidity, common for filter-focused specialty roasts |
| #75 | Moderately Light | Light brown, bright and sweet, origin character easy to taste |
| #65 | Light Medium | Medium brown, more body, acidity starting to round off |
| #55 | Medium | Rich brown, caramel and chocolate notes, a frequent espresso range |
| #45 | Moderately Dark | Dark brown, first spots of oil, roast flavors moving forward |
| #35 | Dark | Very dark brown, oily surface, bittersweet and smoky |
| #25 | Very Dark | Near black and shiny, roast character dominates the cup |
Treat these names as a shared reference point, not a rule. Many specialty roasters draw their own lines, and one company's "medium" can sit a full tile darker than another's. For how each roast level changes flavor in the cup, see our guide on how coffee is roasted to create different flavors.
A color reader earns its place on the bench when every batch gets read the same way. The number itself matters less than how steady it stays from one roast to the next.
Cup a few test roasts, pick the one you like, and record its ground and whole-bean numbers. That becomes the target. Then agree on how far a production batch can drift before someone flags it. Many roasters work with a window of a couple of points either side. Enter your target and a batch reading below to see if the batch is in range and how its gap has moved.
Roast QC tool
Compare a batch against your target roast, on the same scale and with the same sample prep.
Your target
This batch
How we calculate: each reading is compared with its target using your tolerance. The gap is ground minus whole bean, compared with your target gap. Tile names come from the eight SCA roast color tiles (#25 to #95) and apply to ground readings on the Gourmet scale only. Readings only compare fairly when the grind, dish fill and rest time match, so keep your sample grind consistent with lab sieves.
Color shifts slightly as coffee rests and degasses. Read every batch at the same point, for example once it's fully cooled on roast day. Our guide to how long to use coffee beans after roasting covers what happens to beans during that rest.
Put the Agtron reading in the same log as drop temperature, development time and weight loss. Software such as Cropster and Artisan lets you attach the reading to the roast curve. Over a few weeks you'll see which profile changes move the number and which don't.
The reader confirms that you hit the color. It can't tell you the coffee tastes right. Pair your color checks with a regular cupping table set up with the gear from our coffee cupping lab equipment collection.
Two lots can need different profiles to land on the same Agtron number. Moisture and density readings on the green coffee explain a lot of that. The moisture meters and analyzers collection covers the instruments. Our post on using metrics to master your roast shows how color, moisture, density and water activity fit together.
Agtron isn't the only maker, and several readers report on their own scales. Here's how the brands roasters ask about most compare.
| Reader | How it reads | Number it reports | Good fit for |
|---|---|---|---|
| Agtron M-Basic II / III | Near-infrared, benchtop, whole bean or ground | Agtron Gourmet scale | QC labs that want the reference standard |
| Agtron E20-CP | Near-infrared, benchtop, two-point calibration | Commercial or Gourmet scale | Production roasteries matching specs across sites |
| Lighttells CM-100 / CM-200 | Near-infrared, compact, whole bean and ground | Agtron-style numbers | Small and mid-size roasteries starting a QC routine |
| Javalytics | Near-infrared, handheld and benchtop versions | Degree-of-roast readout | Quick checks at the roaster or on the floor |
| ColorTrack R-100B | Laser, ground coffee | ColorTrack scale, where higher numbers mean darker | Roasters already logging ColorTrack data |
| Probat Colorette 4 | Visible-light reflectance, ground coffee | Colorette scale, L*a*b* or a custom scale | Plants running Probat production lines |
Are Lighttells readings the same as Agtron readings? Close, but not one-to-one. Each instrument is consistent with itself, and readings drift between brands. The same goes for any two models. If you switch meters, read 10 to 20 of your own roasts on both before retiring the old one. Build a simple conversion table from those pairs and you keep your history usable.
Color readers turn up on CoffeeTec in both new and used condition. The listings include Agtron M-Basic, M-Basic II, M-Basic III and E20-CP units, plus Lighttells, Javalytics, ColorTrack and LeBrew RoastSee readers. Quote requests for them reach us from roasteries across the United States, Latin America, the Middle East and East Africa. Wherever the buyer is, calibration is the first thing to check.
Before you buy a used unit, ask the seller for:
For a current-model benchmark, compare any used listing against a unit like the Agtron E20-CP roast color meter. If you want a compact reader for a smaller roastery, the Lighttells analyzers and meters collection is a good place to start.
Roasteries upgrade their labs all the time. A shop that moves from a Lighttells to an Agtron, or merges two QC benches into one, often has a working reader sitting in a drawer. Another roaster is usually looking for exactly that unit.
Gather the model, year, reference disks, sample dishes and any calibration paperwork, then take a clear photo of the display mid-reading. CoffeeTec has helped roasters buy and sell equipment since 1972, and sellers list with zero commission. Submit your color analyzer or other roasting equipment and our team will take it from there.
On the Gourmet scale with a ground sample, a light roast usually reads in the 70s and 80s. The SCA tiles place "Light" at #85 and "Moderately Light" at #75. Roasters set their own lines, so check which scale and sample type a number refers to.
The Gourmet scale covers a wider range, and the same coffee reads a higher number on it. The Commercial scale uses a narrower band and is common in high-volume production. M-Basic readers use the Gourmet scale, and the E20-CP can be calibrated to either.
The first number is the whole-bean reading and the second is the ground reading. Whole beans read darker because the outside of the bean roasts faster than the center. The gap between the two shows how evenly the coffee developed.
They're close but not identical. Lighttells meters report Agtron-style numbers, yet each brand's optics and calibration differ slightly. If you move between them, read the same roasts on both and build your own conversion table.
Not to get started. The SCA roast color tiles let you match a ground sample by eye under steady light. Your eye can't separate small differences, though, so a meter becomes worth it once you need repeatable numbers for production or wholesale specs.
Measure once the coffee has cooled to room temperature, and do it at the same point after every roast. Readings shift slightly as coffee rests, so a fixed routine matters more than the exact hour you pick.
There's no single right number. Many espresso roasts sit between the #55 Medium and #45 Moderately Dark tiles on the Gourmet scale, but plenty of specialty espressos roast lighter. Set your target by cupping, then hold it with your color reader.
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