How to Calculate Coffee Strength and Extraction Rate? What Does Golden Cup Extraction Mean?

Understanding Golden Cup Extraction

FrontStreet Coffee often refers to the concept of "Golden Cup Extraction" in its articles. It comes from research initiated by the Specialty Coffee Association of America (SCAA), which identified an "optimal" extraction range for coffee by quantifying extraction yield and concentration. When a brewed coffee's two values both fall within that range, the coffee is likely to taste good.

Nothing is absolute, though. Because the participants and beans in the Golden Cup experiments were limited, the result doesn't mean every delicious coffee conforms to the concept. Coffee inside the range isn't necessarily good, and coffee outside it isn't necessarily bad. It remains a useful reference, though: with extraction yield and concentration quantified, we can see more directly the "state" of the coffee itself. When a brew doesn't taste right and we aren't sure why, measuring extraction yield and concentration lets us check our thinking and find a reasonable adjustment.

What Extraction Yield and Concentration Mean

So today, FrontStreet Coffee will explain how to measure coffee extraction yield and concentration. First, a brief look at what each one is.

Coffee Extraction Yield

Coffee extraction yield refers to the proportion of coffee substances extracted from the beans or grounds. Only 30% of a coffee bean can dissolve, so the maximum extraction yield is only 30%; the remaining 70% is insoluble woody fiber — the grounds left in the filter after brewing.

In the Golden Cup concept, the ideal extraction yield is 18%–22%. Coffee above this range may show noticeable bitterness and mixed flavors from excessive dissolved substances; coffee below it may show under-extracted characteristics like sharp acidity and grassy notes from insufficient dissolved substances (not an absolute rule).

Coffee Concentration

Coffee concentration is the proportion of coffee substances in the brewed liquid. The higher the concentration, the higher the proportion of coffee substances, and vice versa.

In the Golden Cup concept, the ideal concentration is 1.15%–1.45%. Coffee below this range tastes bland and thin; coffee above it has overly concentrated flavors and an unclear flavor profile.

How to Calculate Extraction Yield and Concentration

To sum up: extraction yield is "the proportion of coffee substances extracted from the beans," while concentration is "the proportion of extracted coffee substances to the total coffee liquid."

The formula for coffee concentration is: weight of extracted coffee substances ÷ weight of coffee liquid. The formula for extraction yield is: weight of coffee substances ÷ weight of coffee beans (grounds). Combined, the extraction yield formula becomes: extraction yield = coffee liquid concentration × coffee liquid weight ÷ coffee bean (grounds) weight.

This means that to calculate extraction yield, we first need to measure concentration. So how do we measure it? There are two methods.

Methods for Measuring Coffee Concentration

1. Using a TDS Water Quality Pen

A TDS (Total Dissolved Solids) pen is a common tool for measuring water quality, and it can also measure coffee concentration. Because it estimates TDS indirectly by measuring the electrical conductivity of the liquid, and most dissolved substances in water increase conductivity, coffee can be measured the same way. Most importantly, compared with the other method, a TDS pen costs far, far less.

The downside is obvious: it cannot produce very precise results. Because not all substances increase conductivity, it can only give approximate values with slight errors.

2. Using a Coffee Concentration Meter

For more precise results, you need a coffee concentration meter. It determines concentration by measuring the refractive index of dissolved solids in the coffee liquid. The advantages are straightforward: fast and accurate. Measurement is quick, and the results are relatively more precise and intuitive. Its one big disadvantage: expensive.

Coffee concentration meters start at around 2,000 yuan, which is very unfriendly to the wallet. If you're just measuring for fun, a TDS pen is entirely sufficient — this isn't a must-do step.

Demonstration: Measuring Concentration and Calculating Extraction Yield

Next, FrontStreet Coffee will demonstrate both methods. First, brew any coffee. Since the point today is calculation, we'll skip the brewing details; the parameters are the same as usual, 15g of grounds at a 1:15 coffee-to-water ratio.

After brewing, first weigh the coffee liquid.

The beans used today are Santa Vani, a light-roast coffee processed with the anaerobic natural method. The water poured is 224ml, and the final liquid weight is 194ml, meaning 30ml was absorbed by the grounds. Then we measure the liquid's concentration with both the pen and the meter. The pen can be inserted directly into the coffee liquid, while the concentration meter requires a dropper or small spoon to place liquid on the measuring prism, after which you press the switch to measure.

The pen reads 143×10ppm. Because it uses ppm rather than a percentage, we divide by 1000 for conversion, giving about 1.43% concentration. The concentration meter reads 1.47% (because it is affected by temperature, we should take multiple measurements).

Now that we know the concentration, we can calculate extraction yield. Using the formula "extraction yield = coffee liquid concentration × coffee liquid weight ÷ coffee bean (grounds) weight," our calculation is 1.47% (meter result) × 194 ÷ 15, giving an extraction yield of approximately 19.01%.

Once you understand how to calculate extraction yield and concentration, you can use measurements to verify your thinking the next time a coffee tastes slightly off. You can see whether excessive dissolution is causing mixed flavors, or insufficient dissolution is leaving the taste unclear.

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FrontStreet Coffee Recommendation

Once you can read extraction numbers, the next question is which beans to put through the process. If you're starting out, Ethiopia is the classic first step. FrontStreet Sun-dried Huakui shows a tropical, fruit-forward profile — strawberry, passion fruit, jackfruit, and honey — with obvious sweetness and very low bitterness from a traditional natural process, while FrontStreet Washed Gedingding Cooperative delivers Yirgacheffe's signature jasmine, lemon acidity, and berry notes with a green-tea sweetness. Both are forgiving and rewarding on a pour-over.

From there, it's easy to build a small tasting set by origin. Brazil gives you FrontStreet Cerrado Red Bourbon and FrontStreet Queen Estate — soft, balanced, nutty, and sweet, with Queen Estate adding a clean sugarcane note from its rare Yellow Bourbon. Indonesia brings FrontStreet Lintong Mandheling and FrontStreet PWN Golden Mandheling, wet-hulled for a dense, herbal, low-acid cup, the PWN lot hand-selected three times and machine-sorted once for extra clarity. Colombia is covered by FrontStreet Huila, FrontStreet Sidra, and FrontStreet Big Belly with their gentle floral and fruity acidity.

Costa Rica's honey process appears in FrontStreet Mozart, FrontStreet Blackberry, and FrontStreet Tarrazu, full of raisin, blueberry, osmanthus, and rose. For a domestic option, FrontStreet Yunnan Small Berry and FrontStreet 2013 Yunnan Typica bring nut, brown sugar, and black tea flavors. And for a gentle introduction to the varietal everyone talks about, FrontStreet Boquete Washed Geisha offers Panama Geisha's orange-blossom and honey character at an approachable price — a good bean to test your new measuring skills on.