Reference · roast levels

Coffee roast levels: light, medium, dark — and how to brew each

"Light", "medium" and "dark" sound like a standard, but they are not one. Here is what the roast names, temperatures and colour numbers actually mean, where the SCA, roasters and researchers disagree, and which brewing adjustments are worth trying when you switch roast.

Updated 2026-10-23 · sources listed at the end

What happens as coffee roasts

Green coffee turns yellow, then increasingly darker shades of brown. According to Wikipedia's roasting article, beans lose 15–18% of their mass, mostly water and volatile compounds, while their volume roughly doubles. Two audible events mark the way: first crack at about 196 °C (385 °F), where very light roasts begin, and second crack at about 224 °C (435 °F), when the bean structure turns brittle. Light and medium beans stay dry; oil appears on dark roasts. Coffee also darkens as it ages, the same article notes, so colour alone is a poor guide.

Roast names and bean temperatures

The traditional names, as tabulated by Wikipedia from Coffee Review's glossary (internal bean temperature):

The National Coffee Association (NCA) uses just three categories — light, medium and dark — and says only that beans are brought to "over 400 degrees Fahrenheit". It puts American roast and breakfast blends in medium and Italian and French in dark, and warns that dark-roast names "are often used interchangeably" and that "one roaster's dark coffee may be different than another's".

Colour numbers: tiles and Agtron

Professionals measure roast colour with instruments. A UC Davis team writing in the SCA's 25 magazine describes Agtron analyzers as the de facto standard, giving a number from 100 for very light to 20 for very dark coffee. The same authors say there are "no agreed-upon standards" for roast level: "Some roasters famously sell 'light roasts' darker than the 'dark roasts' produced by other roasters." Among roasters surveyed at the 2023 Roasters Guild Retreat, about half judged roast level by eye.

The numbers also depend on the scale. The SCA's cupping protocol asks for one roast that reads 63.0 on the Agtron "Gourmet" scale, 48.0 on Agtron "Commercial", 62.0 on Colortrack and 96.0 on a Probat Colorette 3b (±1 unit, measured on ground coffee). How four sources draw the lines:

The last row looks darker than the others only because it uses the Commercial scale — the SCA cupping roast reads 15 points lower on it than on Gourmet. Compare numbers only within one scale.

What changes in the cup

The UC Davis authors in 25 cite recent UC Davis research finding that "roast level drove the greatest flavor differences" in filter coffee; the program's drip-brew study roasted one coffee light, medium and dark (Frost and colleagues).

Do dark roasts extract more easily?

The sources disagree.

• Café and roaster guides: Perfect Daily Grind and Clive Coffee say longer, hotter roasting makes beans more porous and soluble, so dark roasts extract more easily and light roasts more slowly.
• Full-immersion lab test: Liang, Chan and Ristenpart (2021) found effectively the same equilibrium strength for light through extra-dark blends, with extraction yields averaging about 23.9% regardless of roast.
• Timed brews: Lindsey and colleagues (2024) brewed two Ethiopian coffees at several roast degrees; extraction yields generally fell for batches that lost more than about 12–14% of their mass in roasting.

The guides describe speed and taste; the studies measured how much ended up in the cup. Neither directly tests the other's claim, so treat "dark extracts faster" as a starting hypothesis to taste-test.

Caffeine: light vs dark

• NCA: light roasts have "a slightly higher amount of caffeine"; dark roast flavor "is not associated with caffeine levels".
• Wikipedia: caffeine is "not significantly affected by the level of roast", but measured by volume a lighter roast contains more because darker beans are less dense.
• Lindsey et al. 2024: under identical brewing, dark roasts generally gave lower caffeine than light and medium roasts; the cup peaked at roasts that lost about 14–16% of their mass, and fell for drop temperatures above about 400–420 °F. At equal extraction yield, dark roasts held more caffeine. Brews ranged from 134–165 mg per 8 oz cup.

How much the brew method itself changes caffeine is covered in caffeine by brew method. None of these sources makes a health claim about roast level.

Brewing adjustments by roast

The SCA's brewing best practices give a single target, not one per roast: water at 200 °F ± 5° (93.0 °C ± 3°) and 55 g/L. Recipe makers then shift things by roast:

Philocoffea's 88 and 83 °C (about 190 and 181 °F, our conversion) sit below the SCA band. A UC Davis study found that at the same strength and extraction, tasters could not tell drip brews at 87, 90 and 93 °C apart; temperature mainly changes how fast coffee extracts (more on the water temperature page). That study used one washed Honduran coffee, and the SCA's summary does not give its roast level.

Weigh, don't scoop. Corrêa and colleagues (2016) measured lower bulk density for a robusta coffee at a moderately dark roast (SCAA #45) than a medium-light one (#65), and Wikipedia makes the same point. A scoop of dark roast holds fewer grams, so set the ratio by weight.

Dialing in a new roast level, step by step

1. Keep your usual recipe and weigh the dose; do not switch scoops.
2. Taste first. Clive Coffee notes that a dark-roast espresso recipe used on a light roast tastes sour and salty; Perfect Daily Grind links long contact with dark roasts to over-extraction and bitterness.
3. Change grind first: a step finer for a lighter roast, a step coarser for a darker one (grind chart).
4. Then temperature, if needed: cooler for dark, hotter for light, within the ranges above.
5. Change one thing per brew and write it down.

Checklist: reading a roast label

• Look for a colour number and its scale (Gourmet or Commercial), not just a word.
• Treat "light", "City" or "French" as the roaster's own scale; names vary by roaster (NCA, SCA 25).
• Note the roast date: colour darkens with age (Wikipedia); freshness is covered on the coffee freshness page.
• Expect oil on dark roasts and a dry surface on light and medium ones.

Roast names vary by roaster and colour numbers by scale, so read every figure here as a reference point. The reliable habit is the same for every roast: weigh, taste, change one variable.