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Extraction · Fundamental

Brewing control chart

The chart that plots brew strength against extraction yield, with brew ratios as diagonal lines and target boxes for filter coffee – where it came from, which targets exist and what sensory research since 2020 has found.

Across the chain: History · Science

Source-checkedby Coffearium verification pass· Last source-checked 20 Oct 2026· Prepared with AI assistance· 13 sources (6 tier A)· 3 contested· Updated 20 Oct 2026
Reading depth
Contents
  • The brewing control chart plots brew strength (total dissolved solids, TDS) against extraction yield; each brew ratio forms a diagonal line on it.1,6
  • It goes back to a 1957 publication by Ernest E. Lockhart of the Coffee Brewing Institute, which placed the “ideal” near 1.25% TDS and 20% extraction.1,5
  • The Golden Cup box of the Specialty Coffee Association (SCA) spans 1.15–1.35% TDS and 18–22% extraction.1
  • The source material does not make clear which consumers or experts found the centre of the chart “ideal”, according to a 2023 synthesis of drip-coffee studies.2
  • In drip-coffee studies from 2020 to 2023, TDS shaped flavour more than extraction yield, and consumers split into two preference groups.1,2

What the chart shows#

The brewing control chart puts two measurements of a brew on one page. Extraction yield runs along the horizontal axis and TDS (total dissolved solids, the brew’s strength) up the vertical axis.1,8 Diagonal lines across the chart mark brew ratios: how much water was used per gram of coffee.2,8 Every brew is one point on it.

The SCA home-brewer standard defines the chart by what it calculates. It is “a chart that allows graphic calculation of brew yield, using brew strength and brew ratio as input.”6 Measure the strength, know the ratio, and the chart gives the yield. The two numbers themselves, and how to measure them, are explained in the extraction yield and TDS entry.

The classic chart adds words to the numbers. It is divided into nine rectangular zones.8 The vertical bands are labelled “strong” and “weak”; the columns run from “under-developed” on the left to “bitter” on the right.1,8 The central zone is labelled “ideal”.1 A 2020 study points out that these labels mix three kinds of word: a judgement (“ideal”), a scale (“weak”, “strong”) and a flavour (“bitter”).1

Reading a brew on the chart#

Each diagonal line holds one brew ratio. Along that line, a stronger brew always means a higher yield, because more of the same dose has dissolved (our calculation from the 2023 formula; see Deep dive).2 At a fixed ratio, only the amount dissolved can change, so the brew moves along its line. Changing the ratio moves the brew to another line.

A worked example (our calculation). Take 30 g of coffee and 500 g of water, a ratio of 60 g per kg. Assume the grounds hold back 2.1 g of liquid per gram, as measured in a 2023 drip study.2 A reading of 1.30% TDS then means about 19.2% extraction, inside the Golden Cup box. A reading of 1.45% at the same ratio means about 21.4%: still inside on yield, but above the box on strength.

The ratio itself is covered in the brew ratio and strength entry.

141618202224260.91.01.11.21.31.41.51.61.7Extraction yield (%)TDS – brew strength (%)50 g/kg55 g/kg60 g/kg65 g/kg70 g/kgGolden Cup1 SCA 310-2021 test target6,2 UC Davis design points2 Lockhart’s “ideal”5
Data table
ValueSource
Golden Cup box18–22% EY; 1.15–1.35% TDS1
SCA 310-2021 test target1.15–1.55% TDS at 55 g/kg (placed on the 55 g/kg line: 18.7–25.3% EY, our calculation)6, 2
Lockhart’s “ideal”≈20% EY; ≈1.25% TDS5
UC Davis design points16, 20, 24% EY × 1.0, 1.25, 1.5% TDS2
Brew-ratio lines50, 55, 60, 65, 70 g coffee per kg water; EY = TDS ÷ (1 − TDS) × (water ÷ dose − 2.1), our calculation2
Our redraw of the brewing control chart, not the SCA artwork. Shown: the Golden Cup box1, the SCA 310-2021 test target on the 55 g/kg line6, Lockhart’s “ideal” point5 and the nine design points of the UC Davis studies.2 Dashed brew-ratio lines (50–70 g of coffee per kg of water) are our calculation, assuming 2.1 g of liquid retained per gram of coffee.2 European and Nordic target boxes are not drawn (see Deep dive). For an interactive chart that places your own brew, see the extraction yield and TDS entry.

Where the chart came from#

The chart dates from the 1950s.2 Ernest E. Lockhart, a biochemist, directed the Coffee Brewing Institute, the research institute of the Pan American Coffee Bureau.8,9,12 In 1957 the institute published his The Soluble Solids in Beverage Coffee as an Index to Cup Quality.1,5 It linked cup quality to strength and extraction yield and combined the two in the chart.1 It placed the “ideal” near 1.25% TDS and 20% extraction.5

A 2021 study cites the publication with the Pan American Coffee Bureau and the National Coffee Association of U.S.A. listed beside Lockhart.5 The chart later passed into the Coffee Brewing Handbook of the Specialty Coffee Association of America (SCAA).1,10 Studies from 2020 and 2023 describe it as the basis of vocational training in the coffee industry.1,2

Who decided what was ideal is not clear. According to the 2023 paper behind the new chart, neither the chart nor its sources show which consumers or experts found the centre “ideal”.2 The original 1957 publication is not openly available, and we have not seen it. An SCAA water handbook describes extensive consumer studies by the Coffee Brewing Center. They concern mineral taste thresholds in water, not the chart.11

The published target boxes#

Golden Cup (SCA). The best-known box spans 1.15–1.35% TDS and 18–22% extraction.1 A 2020 study identifies this central region as the SCA’s Golden Cup Standard.1 The SCAA described the Golden Cup as its certification of high-quality, freshly brewed coffee.11

SCA home-brewer test. SCA Standard 310-2021 tests home brewers at 55 g of coffee per 1.000 kg of water. Its target strength is 1.15–1.55% TDS.6 This is an appliance test, not a statement of what tastes best. On the chart it is a stretch of one ratio line, not a box (see the figure).

European and Nordic boxes. Other boxes, attributed to the former Specialty Coffee Association of Europe and to Norway, circulate on company websites. We found no open primary text for them, so we give no values. The SCA home-brewer standard lists a member of the European Coffee Brewing Centre among its contributors.6

Cupping. The SCA cupping standard uses 8.25 g of coffee per 150 mL of cup capacity.7 That is 55 g per litre (our calculation), the same figure as the home-brewer test ratio. But cupping is an immersion brew, and the chart’s ratio lines assume drip brewing (see Deep dive).

What sensory research found since 2020#

Researchers at the University of California, Davis (UC Davis) re-tested the chart with trained panels and consumers.2,12 The SCA’s Coffee Science Foundation ran the project with the UC Davis Coffee Center, funded by a grant from a brewer manufacturer.12,13 The team brewed drip coffee to nine fixed points: 1.0, 1.25 and 1.5% TDS, each at 16, 20 and 24% extraction.2

  • Strength matters most. In a 2020 study, TDS had the largest effect on the sensory profile and extraction yield a smaller one. Brew temperature had no appreciable effect.1
  • Flavours have their own corners. On the 2023 chart, sour, citrus and red-fruit notes sit at high TDS and low yield. Bitter, astringent and roasted notes sit at high TDS and high yield.2 Sweetness fell as TDS rose, at every roast degree tested.3
  • Consumers disagree with each other. In the 2023 synthesis, 57% of consumers liked low-TDS coffees best, with liking peaking at 18% extraction.2 The other 43% had two favourite regions.2

The authors propose a new Sensory and Consumer Brewing Control Chart to replace the classic one.2 It shows where flavours peak and where each consumer group is happiest, instead of one “ideal” box.2 As of October 2026, no SCA standard opened for this entry replaces the Golden Cup values. SCA 310-2021 refers to “the latest version” of the SCA chart without reproducing it.6

The mass balance behind the lines#

The ratio lines follow from conservation of mass; according to the UC Davis group, this is all the quantitative content of the chart.8 For drip brewing, the 2023 chart paper calculates extraction yield (PE) from the brew ratio Rbrew (water ÷ coffee) and a liquid retention ratio Rabs ≈ 2.1:2

PE = TDS ÷ (1 − TDS) × (Rbrew − Rabs)

With TDS as a fraction, each ratio gives a nearly straight line through the origin (our calculation). Three consequences follow (our calculation, with Rabs = 2.1):

  • The Golden Cup box spans a band of ratios. Its corners are reached between about 48 g of coffee per kg of water (22% at 1.15% TDS) and about 66 g per kg (18% at 1.35% TDS). Outside that band, no grind or time setting puts a drip brew into the box.
  • The 55 g/kg line runs through the box. At 1.15% TDS it gives 18.7% extraction, at 1.35% it gives 22.0%: almost the box’s diagonal.
  • The SCA 310 test target reaches beyond 22%. At 55 g/kg, 1.15–1.55% TDS corresponds to about 18.7–25.3% extraction. The real figure depends on how much liquid a given brewer’s grounds retain.

The retention ratio is measured, not fixed. It was about 2.1 g/g in the 2023 drip work2; immersion grounds held 2.48 ± 0.19 g/g in another study.5 A brewer with a different retention shifts every line.

Sensory studies across the chart#

Design. The 2020 temperature study brewed one coffee to nine positions on the chart at 87, 90 and 93 °C. It kept the water at 3,075 g and set the ratio by changing the dose.1 Twelve panellists, aged 19–30, were trained on all samples.1 A second 2020 study crossed the same TDS and yield levels with three roast degrees, giving 27 coffees.2,3 Of 30 attributes rated, 21 differed significantly across the brews.3

Which factor matters. A multivariate analysis of variance in the temperature study gave the largest F-ratio for TDS, then extraction yield, then their interaction; all three were significant.1 Temperature and its interactions were not.1

0123456F-ratioTDS5.44 · p < 0.0011 Extraction yield (PE)2.46 · p < 0.0011 TDS × PE1.56 · p < 0.0011 Brew temperature1.25 · p = 0.111 Temperature × TDS1.16 · p = 0.141 Temperature × TDS × PE1.10 · p = 0.171 Temperature × PE1.07 · p = 0.301
Data table
F-ratioSource
TDS5.44 · p < 0.0011
Extraction yield (PE)2.46 · p < 0.0011
TDS × PE1.56 · p < 0.0011
Brew temperature1.25 · p = 0.111
Temperature × TDS1.16 · p = 0.141
Temperature × TDS × PE1.10 · p = 0.171
Temperature × PE1.07 · p = 0.301
How strongly each factor changed the sensory profile of drip coffee in one 2020 study: F-ratios from a multivariate analysis of variance, with p-values, as reported. Larger F means a larger effect relative to noise; p < 0.05 is significant.1

Attributes. In the temperature study, five attributes rose with TDS only: bitter, astringent, rubber, earthy and viscous.1 Sour, citrus, berry and fruity rose towards lower yield, and black tea fell with TDS but rose with yield.1 In the roast study, sweetness was inversely correlated with TDS at every roast degree.3 According to the group’s SCA magazine article, bitterness for a medium roast rose with both TDS and yield (see Contested).8 The same article argues that most experts could not taste the difference between two brews just either side of a zone boundary, though the classic chart puts them in different zones.8

Consumers. A 2021 study served the 27 brews of the temperature study to 118 mostly college-age consumers of black coffee.2,4 Cluster analysis found two segments whose preferences varied most with TDS; liking formed a dome for one segment and a saddle for the other.4 The 2023 synthesis gives the split as 57% and 43%.2 The larger segment liked the lower left of the chart best: low TDS, low to medium yield.2 The smaller one liked low yield with medium to high TDS, and high yield with medium TDS.2 Over the three studies, the group collected 32,076 descriptive measurements and 3,186 liking ratings on the 9-point hedonic scale.2

Limits of the chart#

  • Drip coffee only. The 2023 chart was built from drip brews; it does not show the effects of variety, origin or other brewing factors.2
  • Not for immersion. In full immersion, yield settles at an equilibrium of about 21% over a wide range of ratios.5 Changing the ratio then moves the brew up or down, not along a drip ratio line.5 Cupping-style brews in the same study reached 23.9 ± 0.6% (caffeinated coffee).5
  • Not for espresso. The 2023 chart covers drip coffee only.2 No comparable sensory and consumer map for espresso was found among the sources opened for this entry; the extraction yield and TDS entry gives espresso strengths.
  • One population. The consumer data come mainly from young adults in Northern California. The authors expect drinkers elsewhere could segment differently.2
  • Sharp lines. Zone boundaries are drawn as steps, yet according to the UC Davis group most experts could not tell apart two brews just either side of a boundary.8

Reference values#

Parameter Value Context Source
Golden Cup box (SCA) 1.15–1.35% TDS; 18–22% extraction Central “ideal” region of the classic chart Batali et al.1
Lockhart’s “ideal” TDS near 1.25%; extraction near 20% Coffee Brewing Institute, 1957 Liang et al.5
SCA 310-2021 test target 1.15–1.55% TDS at 55 g coffee per 1.000 kg water Home-brewer certification SCA6
SCA 310 target as extraction ≈18.7–25.3% Our calculation, Rabs = 2.1 from SCA6, Guinard et al.2
Ratios that reach the Golden Cup box ≈48–66 g coffee per kg water Drip; our calculation, Rabs = 2.1 from Batali et al.1, Guinard et al.2
Cupping ratio 8.25 g per 150 mL (= 55 g/L, our calculation) SCA cupping standard SCA7
“Good” yield range 18–22% Long-standing industry range Mestdagh et al.10, Batali et al.1
UC Davis design points TDS 1.0, 1.25, 1.5%; extraction 16, 20, 24% Drip coffee; three roast degrees Guinard et al.2
Liquid retention ratio, drip ≈2.1 g per g coffee Basis of the 2023 ratio lines Guinard et al.2
MANOVA F-ratios TDS 5.44; PE 2.46; TDS × PE 1.56 (all p < 0.001); temperature 1.25 (p = 0.11) 87, 90, 93 °C; nine chart positions Batali et al.1
Attributes that differed 21 of 30 Three roast degrees × nine positions Frost et al.3
Trained panel 12 panellists, aged 19–30 Temperature study Batali et al.1
Consumers 118, mostly college-age; two segments The 27 brews of the temperature study Cotter et al.4, Guinard et al.2
Consumer segments 57% (low TDS, peak at 18% extraction); 43% (two optima) 2023 synthesis Guinard et al.2
Equilibrium yield, immersion About 21% Wide range of brew ratios Liang et al.5
Cupping-style yield 23.9 ± 0.6% (caffeinated) Immersion at equilibrium Liang et al.5

The history in more detail#

What is documented. Lockhart’s 1957 publication is the origin cited by every research paper opened for this entry.1,2,5 According to an SCA column, Lockhart’s hypothesis was that beverage quality could be estimated by measuring TDS and calculating extraction.9 According to the same column, the chart let a user classify a coffee as “strong”, “weak”, “under-developed” or “ideal”.9 A 2017 textbook chapter cites the chart from the SCAA Coffee Brewing Handbook. It describes 18–22% as a range “generally considered” good “for quite a long time”.10 The SCAA’s 2011 water handbook adapts a figure from the same handbook’s brewing chart.11

What is not. We could not open the 1957 text, so we cannot say how many people tasted, who they were, or how the box edges were chosen. The 2023 paper could not say either.2 Claims that the box came from a particular consumer panel are not supported by any source opened for this entry. A 2017 textbook chapter suggests that preferences have since moved from the drip-filter profile, once the standard, towards espresso-type coffees.10

From one box to a map. The UC Davis work kept the axes and the mass balance but replaced the hedonic labels with measured attribute and liking surfaces.2 According to an SCA column, the work both confirmed that changing TDS and yield changes flavour predictably and built on Lockhart’s chart.9

Open questions#

  • Origin of the classic box. Without open access to the 1957 publication, the panel behind the “ideal” region is unknown.2
  • Regional targets. No peer-reviewed or standards text for the European and Nordic boxes was found; whether they rest on their own sensory data is not established.
  • Preference beyond one population. The two consumer segments come from one region; no study opened for this entry tested them elsewhere.2
  • Other coffees and methods. The 2023 chart rests on a few drip-brewed coffees; how far the flavour map shifts with origin, process or roast style beyond the three roasts tested is open.2
  • Optimal yield. According to a 2017 textbook chapter, optimal yields outside 18–22%, mostly higher, have been reported for several methods, and good research on this question remains to be done.10

Key studies#

Batali et al., 2020 – Temperature at fixed strength and yield. Brewed one coffee to nine positions on the classic chart at three temperatures and tested the brews with a trained panel. TDS and extraction yield both changed the sensory profile, TDS more strongly; brew temperature had no appreciable effect once both were fixed.

Scientific Reports 10, 16450 · doi:10.1038/s41598-020-73341-4

Frost et al., 2020 – Strength, yield and roast. Crossed three TDS levels, three yields and three roast degrees in drip coffee and mapped 30 attributes with response surfaces. Most attributes differed across the brews, and sweetness fell as strength rose regardless of roast.

Journal of Food Science 85(8), 2530–2543 · doi:10.1111/1750-3841.15326

Cotter et al., 2021 – Consumer preferences across the chart. Asked 118 black-coffee drinkers to rate brews from across the chart. Two segments emerged whose liking depended mainly on TDS, and the authors argue that the notion of an “ideal” coffee should be reconsidered.

Journal of Food Science 86(1), 194–205 · doi:10.1111/1750-3841.15561

Guinard et al., 2023 – A new control chart. Combines the UC Davis drip-coffee studies into a Sensory and Consumer chart that shows where attributes peak and where each consumer segment finds its optimum. The authors note that the source of the classic “ideal” box is unclear and propose that the new chart replace it.

Journal of Food Science 88(5), 2168–2177 · doi:10.1111/1750-3841.16531

Liang et al., 2021 – Immersion at equilibrium. Models full immersion brewing as desorption to equilibrium. Yield settles near 21% over a wide range of ratios, so immersion brews move vertically on the chart when the ratio changes, unlike drip brews.

Scientific Reports 11, 6904 · doi:10.1038/s41598-021-85787-1

Contested
  • Where the “ideal” lies: the SCA Golden Cup box puts it at 1.15–1.35% TDS and 18–22% extraction1; a 2021 consumer study found preferences spread over a wide range of strengths and yields and argued that “ideal” coffee should be reconsidered4, and in the 2023 synthesis the larger consumer group liked low-TDS coffees best, with liking peaking at 18% extraction.2
  • Upper strength limit for filter coffee: the Golden Cup box ends at 1.35% TDS1, while the SCA home-brewer standard accepts up to 1.55% TDS at its test ratio.6 The two serve different purposes – a quality target and an appliance test.
  • Bitterness and extraction yield: in a 2020 study at three brew temperatures, bitterness rose with TDS only1; an SCA magazine article by the same research group reports that, for a medium roast, bitterness in general rose with both TDS and extraction yield.8 The two analyses rest on different sets of brews.
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Change log

  • – Removed the 17.9% vs 18.1% extraction example (two places); the point is kept without numbers. Reason: The figures rested on one Tier B source (SCA magazine) only.
  • – The consumer study is now said to have tasted the 27 brews of the temperature study, not the roast study's 27 coffees. Reason: Guinard et al. 2023 state that the consumers rated the temperature-study brews.
  • – Bitterness result of the SCA magazine article narrowed to a medium roast (contested item and Attributes paragraph). Reason: The article's analysis uses medium-roast data only, not all the group's studies.

Sources

  1. ABatali, 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. doi:10.1038/s41598-020-73341-4 · other copies
  2. AGuinard, 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(5), 2168–2177. doi:10.1111/1750-3841.16531 · other copies
  3. AFrost, S. C.; Ristenpart, W. D.; Guinard, J.-X. (2020). Effects of brew strength, brew yield, and roast on the sensory quality of drip brewed coffee. Journal of Food Science 85(8), 2530–2543. doi:10.1111/1750-3841.15326 · other copies
  4. ACotter, A. R.; Batali, M. E.; Ristenpart, W. D.; Guinard, J.-X. (2021). Consumer preferences for black coffee are spread over a wide range of brew strengths and extraction yields. Journal of Food Science 86(1), 194–205. doi:10.1111/1750-3841.15561 · other copies
  5. ALiang, J.; Chan, K. C.; Ristenpart, W. D. (2021). An equilibrium desorption model for the strength and extraction yield of full immersion brewed coffee. Scientific Reports 11, 6904. doi:10.1038/s41598-021-85787-1 · other copies
  6. ASpecialty Coffee Association (2021). SCA Standard 310-2021 Home Coffee Brewers: Specifications and Test Methods. Specialty Coffee Association.
  7. A/BSpecialty Coffee Association (2024). SCA Standard 102-2024 Coffee Value Assessment: Sample Preparation and Tasting Mechanics. Specialty Coffee Association.
  8. BFrost, S.; Batali, M.; Guinard, J.-X.; Ristenpart, W. D. Towards a New Brewing Chart. Specialty Coffee Association, 25 Magazine, Issue 13.
  9. BCarmichael, L. (column hosted by Giuliano, P.) Coffee, Decoded: The Science of “Dialling-In”. Specialty Coffee Association.
  10. BMestdagh, F.; Glabasnia, A.; Giuliano, P. (2017). The Brew – Extracting for Excellence. In: Folmer, B. (ed.), The Craft and Science of Coffee, Academic Press, ch. 15, pp. 355–380. doi:10.1016/B978-0-12-803520-7.00015-3 · other copies
  11. A/BBeeman, D.; Songer, P.; Lingle, T. (ed. Everage, L.) (2011). The Water Quality Handbook (ISBN 978-1-882552-08-5). Specialty Coffee Association of America.
  12. BPooler, F.; Fresh Cup; UC Davis College of Engineering Communications (2025). UC Davis Coffee Center Contributes Research to New Brewing Control Chart. University of California, Davis, Coffee Center.
  13. BSpecialty Coffee Association; Coffee Science Foundation Towards a Greater Understanding of Coffee Brewing Fundamentals. Specialty Coffee Association.

Tier A · authoritative · B · trade and expert · C · general. Supporting quotes for every source are in the data version of this entry. If a publisher’s site refuses access, try the doi link or “other copies”.

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