Roast Color Explained: Agtron Numbers and What They Mean
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You may have spotted something like “Agtron 55/68” in a coffee review or on a specialty roaster’s bag and wondered what it meant. What do Agtron numbers mean? They’re a measurement of roast color: an instrument shines light on a sample of roasted coffee and scores how much it reflects. Higher numbers mean lighter roasts; lower numbers mean darker roasts. The first number is usually the whole bean reading, the second the ground coffee reading. Together they give a far more precise picture than words like “medium” or “French,” which mean different things to different roasters.
This guide explains how roast color is measured, how to read the numbers, and why two official-looking charts can give the same number different names.
Key takeaways
- Agtron numbers measure how much light roasted coffee reflects; the smaller the number, the darker the roast.
- A reading like 55/68 means whole bean 55, ground 68. Ground coffee usually reads lighter because the bean’s interior is less developed than its surface.
- Coffee Review classifies 60–70 as medium and 50–60 as medium-dark; a 2004 USDA purchasing standard calls 50–60 medium. The labels differ, the numbers don’t.
- Readings vary between instruments and scales, so compare numbers only from the same source.
In this article
- What do Agtron numbers mean?
- How to read a reading like 55/68
- Roast names by Agtron number: two charts
- Why roast color matters in the cup
- FAQ
What do Agtron numbers mean?
Agtron is a company that makes roast color analyzers, and its name has become shorthand for the measurement, much as people say “Kleenex” for tissues. According to Coffee Review, which publishes Agtron readings with its reviews, the instruments are near-infrared spectrophotometers: they bounce light off a sample and assign it a value. Darker coffee absorbs more light and reflects less, so it gets a lower number.
Why not just look at it? Because human eyes are easily fooled by lighting, bean size, oil on the surface and the color of the bag. An instrument gives the same reading in a dark warehouse or a sunny café, which lets roasters repeat a profile batch after batch.
Other color readers
Agtron isn’t the only brand. Coffee Review lists other color readers, including Javalytics, Probat’s Colorette and HunterLab instruments. Each is consistent with itself but may not match the others exactly, and even Agtron has more than one scale: Coffee Review notes that its M-Basic reads on the “Gourmet” scale while other models read on a “Commercial” scale. So a number is only meaningful alongside its instrument and scale.
How to read a reading like 55/68
| Part | Meaning | Example |
|---|---|---|
| First number | Whole bean color (the outside of the bean) | 55 |
| Second number | Ground coffee color (outside and inside mixed) | 68 |
| Difference (delta) | How evenly the bean is roasted from surface to core | 68 − 55 = 13 |
| Average | What Coffee Review uses to name the roast | (55 + 68) ÷ 2 = 61.5 → medium |
Why ground coffee reads lighter
A bean roasts from the outside in. The surface browns first; the center lags behind. When you grind it, the lighter interior mixes in, so the ground number is almost always higher than the whole bean number. According to Coffee Review, darker roasts usually show a narrower gap, because the heat has had time to reach the core. Lighter roasts show a wider one.
Worked example
Two coffees both read 60 as whole beans.
- Coffee A grinds to 64 (delta 4): fairly even development, likely a slower or longer roast.
- Coffee B grinds to 76 (delta 16): dark-ish outside, much lighter inside. It may taste roasty at first sip and then sharper or grassier as it cools.
Same whole bean color, different cups. That’s why serious reviewers publish both numbers.
Roast names by Agtron number: two charts
Here’s where it gets confusing. Different organizations attach different names to the same numbers.
| Agtron number | Coffee Review (Gourmet scale, average of bean and ground) | USDA purchasing standard (2004) |
|---|---|---|
| Above 80 | Light | Light (80–90) |
| 70–80 | Medium-light | Not defined |
| 60–70 | Medium | Not defined |
| 50–60 | Medium-dark | Medium |
| 40–50 | Dark | Moderately dark |
| 25–40 | Very dark | Dark (30–40) |
| Below 25 | Extreme dark | Not defined |
The USDA document is a federal Commercial Item Description for buying coffee (A-A-20213B, dated August 2004). It reflects a commercial view of roasting, where “medium” sits darker than in specialty coffee. Neither chart is wrong; they simply describe different markets. The lesson: if you want to compare coffees, compare numbers from the same source, not labels.
Why roast color matters in the cup
| Roast color | Typical flavor direction |
|---|---|
| Light (high numbers) | Bright acidity, fruit, floral notes, lighter body; origin character comes through |
| Medium | Balance of acidity and sweetness, caramel, nuts, chocolate |
| Medium-dark | Fuller body, bittersweet chocolate, less acidity |
| Dark (low numbers) | Roasty, smoky, bittersweet; origin flavors recede; oil may appear on beans |
Color is a result of the chemistry happening inside the bean, including the browning reactions explained in the Maillard reaction in coffee roasting. For the everyday version of this topic, see light vs medium vs dark roast, and if you’ve heard that dark roast has more caffeine, read the dark roast caffeine myth.
Can you measure roast color at home?
Not precisely without an instrument, but you can be consistent. Compare beans side by side under the same daylight, grind a small sample to check the inside, and note the roast stage you stopped at if you roast yourself (our guide on how to roast coffee at home covers this).
Our roasts, from light to darkest
We describe our roasts in words rather than publishing Agtron numbers, so here’s how they line up from lighter to darker. Blonde is our light, caramel-sweet blend from Central America and Africa. Medium Blend is a well-balanced medium roast. French Roast is our classic dark roast with bittersweet chocolate and low acidity, and Italian Roast is our darkest, a smoky Arabica and Robusta blend with a thick crema. All are roasted 1–5 days before delivery.
Agtron numbers FAQ
Is a higher Agtron number lighter or darker?
Lighter. Higher numbers mean the coffee reflects more light. Lower numbers mean darker roasts.
What Agtron number is a medium roast?
It depends on the chart. Coffee Review calls an average of 60–70 medium; the 2004 USDA purchasing standard calls 50–60 medium.
Why are there two Agtron numbers?
One is the whole bean reading and the other the ground reading. Ground coffee reads lighter because the bean’s interior is less roasted than its surface.
Do roasters have to publish Agtron numbers?
No. It’s optional and mostly used by specialty roasters and reviewers. Many roasters use color readers internally for quality control.
Does roast color affect caffeine?
Only slightly. Differences in caffeine between roast levels are small and depend on whether you measure by weight or by volume.
Sources
- Agtron Numerology, Coffee Review
- Roast Definitions, Coffee Review
- Commercial Item Description A-A-20213B: Coffee, USDA Agricultural Marketing Service, 2004
Facts checked in October 2026.
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