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Reference · brewing control chart

The brewing control chart, explained

The coffee brewing control chart plots how strong a cup is against how much of the coffee dissolved into it. Its 1957 “ideal” box still anchors most brewing advice; UC Davis research published from 2020 to 2023 redrew it around flavor and consumer liking. To put your own brew on the chart, use the extraction yield calculator.

Updated 2026-10-15 · sources listed at the end

The chart at a glance

ElementWhat it showsClassic value
Vertical axisStrength: total dissolved solids (TDS), % of the drink’s mass1.15–1.35% in the box
Horizontal axisExtraction: percent of the dry grounds that dissolved (PE, also EY)18–22% in the box
Diagonal linesBrew ratio — the two axes are linked by itgrams of grounds per liter of water
Nine zonesStrong / weak rows × under-developed / bitter columns, “ideal” in the center3 × 3 grid

Where the chart came from

The chart traces to Ernest Earl Lockhart, a biochemist with a 1939 MIT doctorate who later directed the Coffee Brewing Institute. Fresh Cup reports that the institute was set up in the early 1950s by the National Coffee Association and the Pan American Coffee Bureau. Lockhart’s 1957 paper, “The Soluble Solids in Beverage Coffee as an Index to Cup Quality,” proposed that cup quality could be indexed by how much of the grounds dissolve. According to SCA 25 magazine, the SCA Brewing Handbook and SCA classes are built around the resulting chart, and Fresh Cup notes the SCA has taught with it since the 1980s.

How to read the classic chart

As the UC Davis authors explain, the chart’s values follow from mass conservation: TDS and percent extraction are tied together by the brew ratio, drawn as diagonal lines. Along any one line, Wikipedia notes, extraction and strength are directly proportional.

  1. Find the column (extraction). Below 18% the chart reads “under-developed,” usually interpreted as sour or grassy; above 22% it reads “bitter.”
  2. Find the row (strength). Above the box is “strong,” below it “weak.”
  3. Read the zone. The labels combine, giving nine rectangles; the center one is labeled “Ideal – Optimal Balance.”
  4. Check the ratio line. Your brew sits on the diagonal for the ratio you used; changing strength at the same extraction means moving to another ratio line.
Schematic of the classic brewing control chart layout Extraction across, TDS up. Two vertical lines at 18 and 22 percent extraction and two horizontal lines at 1.15 and 1.35 percent TDS divide the chart into nine zones. The center zone is shaded as the classic ideal box. A diagonal line through the center of the box shows one brew-ratio line. Numbered markers 1 to 6 match the list below. 1.151.35 1822 extraction, % → TDS, % ↑ 1 2 3 4 5 6
  1. Classic “ideal” box — 18–22% extraction, 1.15–1.35% TDS.
  2. Under-developed column — extraction below 18%; read as sour or grassy.
  3. Bitter column — extraction above 22%.
  4. Strong row — TDS above 1.35%. Corner zones combine labels, e.g. strong and bitter.
  5. Weak row — TDS below 1.15%.
  6. A brew-ratio line — on one ratio, TDS and extraction rise together. This one runs through the box center (20%, 1.25%).
Original schematic drawn by pourxlab.com from the zone description in SCA 25 (source 1) and the box values in Batali et al. 2020 and Fresh Cup (sources 5 and 9); it is not a copy of the published chart. Box and axes to scale; the ratio line is illustrative.

One chart, several boxes

The box is a convention. Wikipedia lists three regional standards, and SCA’s home-brewer standard uses a wider strength band.

StandardRatioStrength (TDS)Source
North American55 g/L (18:1)1.15–1.35%; 1.25% in the ratio tableWikipedia
European58 g/L (17:1)1.20–1.45%; 1.35% in the ratio tableWikipedia
Nordic63 g/L (16:1)1.30–1.50%; 1.40% in the ratio tableWikipedia
SCA Standard 310-2021 (home brewers)55 g per 1.000 kg water1.15–1.55%SCA

The 55 g/L figure is the same reference used in the coffee-to-water ratio guide and the printable ratio chart.

What was wrong with the 1957 box

The UC Davis Coffee Center team set out three criticisms in SCA 25:

  • It mixes description with preference, assuming one ideal for every drinker.
  • Its edges are too sharp. Rectangles imply that 17.9% and 18.1% extraction taste different; most experts could not tell them apart.
  • It is flavor-poor: only bitter and under-developed stand in for the many flavors now recognized.

The UC Davis studies

The work began in 2017 as a Coffee Science Foundation and UC Davis Coffee Center project underwritten by a Breville grant. Drip brews were made at three target strengths (about 1%, 1.25% and 1.5% TDS) crossed with three extraction levels (about 16%, 20% and 24%), one brew in each of the classic chart’s nine zones, on a Curtis G4 commercial brewer using a wet-processed Honduran coffee. Twelve trained panelists rated 30 attributes from the World Coffee Research lexicon on a 0–100 scale, in triplicate, producing more than 58,000 sensory data points.

PaperWhat it testedKey result
Frost, Ristenpart & Guinard 2020, J. Food Sci. 85(8)TDS × extraction at light, medium and dark roastFlavor trends across the chart (below)
Batali, Ristenpart & Guinard 2020, Sci. Rep. 10Brew water at 87, 90 and 93 °C, TDS and extraction fixedTemperature had “no appreciable impact” on sensory profile
Cotter, Batali, Ristenpart & Guinard 2021, J. Food Sci. 86(1)118 consumers, 27 coffees, 3 sessionsTwo preference clusters; differences mostly a function of TDS
Guinard et al. 2023, J. Food Sci. 88Combines the three data setsThe new Sensory and Consumer chart

Where the flavors sit

  • Bitterness rises with both TDS and extraction, peaking top right — agreeing with Lockhart. Burnt/ashy follows the same direction at lower intensity.
  • Sourness rises with TDS and falls with extraction, peaking top left — consistent with “under-developed.”
  • Sweetness falls with both TDS and extraction, peaking bottom left. So “weak” is a misleading label for a corner where sweetness is highest.
  • Dark chocolate, in some roasts, falls with TDS and rises with extraction, peaking bottom right.
Schematic of the UC Davis findings on the brewing control chart Same axes as figure 1. Nine dots mark the target brews at about 1, 1.25 and 1.5 percent TDS and 16, 20 and 24 percent extraction. The classic box is dashed and labeled classic standard. Shaded corner areas show where sour, bitter, sweet and dark chocolate notes peaked. Markers show where the two consumer clusters liked coffee most. Numbered markers 1 to 8 match the list below. 1.01.251.5 16182024 extraction, % → TDS, % ↑ 1 2 3 4 5 6 7 8 8
  1. Target brews — about 1%, 1.25% and 1.5% TDS × 16%, 20% and 24% extraction.
  2. Sour peaks at high TDS, low extraction (with citrus and fruit notes).
  3. Bitter peaks at high TDS, high extraction (with astringent and roasted notes).
  4. Sweet peaks at low TDS, low extraction.
  5. Dark chocolate (some roasts) peaks at low TDS, high extraction.
  6. “Classic standard” — the 1957 box, relabeled in the new chart.
  7. Cluster 1 (57% of consumers) — liking rose as TDS fell and peaked at 18% extraction.
  8. Cluster 2 (43%) — two liking peaks: low extraction with medium-to-high TDS, and high extraction with medium TDS.
Original schematic drawn by pourxlab.com from SCA 25 (source 1), Guinard et al. 2023 (source 2) and Batali et al. 2020 (source 5). Dots and the dashed box are placed to scale; the shaded flavor areas and cluster markers show direction only and are not to scale.

The new chart

Guinard and colleagues published the Sensory and Consumer Brewing Control Chart in the Journal of Food Science in 2023; UC Davis and Fresh Cup publicized it in December 2024 and January 2025. It comes in four versions: a Sensory chart (12 attributes, each placed where it peaks, with font size showing intensity), a Consumer chart with the two preference clusters, a combined chart, and a streamlined chart close to Lockhart’s layout. The streamlined version shows brew ratio as grams of water per gram of grounds, places up to two attributes in each corner, and keeps the 1957 box as the “classic standard” rather than “ideal.” The authors write that “The ‘ideal’ coffee represented in the classic BCC, therefore, is misleading, and quite possibly, inaccurate.”

Its limits: drip coffee only, and consumers who were mostly young adults in Northern California. Ristenpart told Fresh Cup that the middle of the chart is better described as “the coffee that displeased the least people.” Guinard has said he would like a similar chart for espresso.

Using it at home

  • No refractometer: weigh coffee and water and find your ratio line; Ristenpart notes you won’t know exactly where on it you are.
  • Move along the line: finer grinds brew more slowly and give higher TDS; coarser grinds do the opposite.
  • Chasing sweetness? Head toward the lower left. Too bitter? You are likely toward the upper right.
  • Immersion brews: UC Davis modeling suggests strength is easier to control with the ratio than with extraction.
  • With a refractometer: enter TDS, dose and beverage weight in the extraction yield calculator to get your exact point.

Sources

  1. Frost S., Batali M., Guinard J.-X., Ristenpart W.D. — Towards a New Brewing Chart. SCA 25 Magazine, Issue 13 (Lockhart history, nine zones and labels, criticisms, study design, attribute trends)
  2. Guinard J.-X., Frost S., Batali M., Cotter A., Lim L.X., Ristenpart W.D. (2023) A new Coffee Brewing Control Chart relating sensory properties and consumer liking to brew strength, extraction yield, and brew ratio. Journal of Food Science 88, 2168–2177, doi:10.1111/1750-3841.16531 (open-access copy hosted by the University of Oregon)
  3. Cotter A., Batali M., Ristenpart W., Guinard J.-X. — Consumer preferences for black coffee are spread over a wide range of brew strengths and extraction yields. ASIC 2021 e-poster (118 consumers, 27 coffees, two clusters)
  4. Ristenpart W., Cotter A.R., Guinard J.-X. (2023) Consumer preference data for black coffee. Dryad dataset (118 consumers × 27 coffees; related Journal of Food Science 2021 paper)
  5. Batali M.E., Ristenpart W.D., Guinard J.-X. (2020) Brew temperature, at fixed brew strength and extraction, has little impact on the sensory profile of drip brew coffee. Scientific Reports 10, 16450
  6. UC Davis Coffee Center — Publications (DOIs 10.1111/1750-3841.15326 and 10.1111/1750-3841.15561)
  7. UC Davis Coffee Center — UC Davis Coffee Center contributes research to new brewing control chart (January 2, 2025)
  8. SCA / Coffee Science Foundation — Towards a Greater Understanding of Coffee Brewing Fundamentals (two-year project, Breville grant)
  9. Pooler F. — Why the New Coffee Brewing Control Chart is a Big Deal. Fresh Cup, December 18, 2024
  10. Global Coffee Report — The Coffee Brewing Control Chart 2.0
  11. Wikipedia — Coffee extraction (regional strength ranges, 55/63/58 g per liter table)
  12. SCA Standard 310-2021, Home Coffee Brewers (1.15–1.55% strength at 55 g coffee per 1.000 kg water)