Extraction yield

Extraction yield is the share of the dry coffee grounds that dissolved into the finished drink, given as a percentage by weight. Grind 20 grams of coffee, brew it, and if 4 grams of that mass ended up dissolved in the liquid, you extracted 20%. The rest — spent grounds — goes in the bin.

It is sometimes called solubles yield, and in brewing conversation it is usually shortened to EY. Wikipedia’s definition is the plainest one going: “what percentage (by weight) of the grounds are dissolved in the water.”¹

There is a ceiling, and it is nowhere near 100%

A roasted coffee bean is mostly not dissolvable. The trade publication Fresh Cup puts the soluble fraction at “about 30 percent of roasted coffee”;² the other ~70% is cell-wall material — cellulose and similar structure — that water cannot lift out no matter how long you brew.

So the practical range runs from 0% to roughly 30%, and the conventional target sits in the upper-middle of it: 18–22%. That band is the single most repeated number in brewing, and it holds across independent sources — Wikipedia gives it as “20±2% (18–22%)”,¹ Fresh Cup as “target extraction ranges between 18 and 22 percent”,² and the equipment-care company Urnex as “ideal extraction of a brewed coffee occurs between 18 and 22 percent.”³

Aiming below the full 30% is deliberate. The compounds that come out last are the harsh, drying, woody ones; stopping around 20% is a bet that you have taken the sweetness and the acidity and left the worst of the bitterness behind in the grounds.

How you actually get the number

You cannot weigh dissolved coffee directly, so you infer it. You need three things: the dose (dry coffee, in grams), the brew weight (the finished liquid, in grams), and the TDS of that liquid, read off a refractometer.

Extraction yield (%) = TDS (%) × brew weight (g) ÷ dose (g)

Worked through: 20 g of coffee producing 320 g of drink at 1.30% TDS gives 1.30 × 320 ÷ 20 = 20.8%.

That arithmetic is also the reason extraction and strength are not the same thing, which is the most common confusion around the word. Strength is how concentrated the cup is. Extraction is how thoroughly you emptied the grounds. A weak cup can be heavily extracted and a strong cup barely extracted — it depends entirely on how much water you put in, which is the job of the brew ratio.

The three lock together in a simple proportion that Wikipedia states outright: Strength ∝ Brew ratio × Extraction.¹ Fix any two and the third is determined. The roasting consultant Scott Rao makes the same point from the other direction — “each particular combination of EY and TDS can only be achieved by a unique brewing ratio.”⁴

What moves it

Four levers, all of them ways of changing how much coffee surface the water reaches and for how long:

• Grind size — finer grounds have vastly more surface area, so they give up solubles faster. This is the main dial on an espresso machine and on a competition brew bar alike.
• Water temperature — hotter water dissolves more, faster. Fresh Cup, citing the Specialty Coffee Association, gives “the ideal brewing temperature to be between 195 and 205 degrees Fahrenheit”² (about 91–96 °C).
• Contact time — longer steeping or a slower drawdown pulls more out.
• Agitation — stirring, pouring turbulence, or the swirl at the end of a pour-over refreshes the water touching each particle.

One important limit on all of this: it applies to percolation brewing, where water passes through a bed of grounds. For full-immersion brewing — French press and the like — the research summarised in this wiki’s Total dissolved solids note found extraction yield staying essentially fixed around 21% no matter how the brew ratio, temperature or grind changed. With an immersion brewer you are largely choosing strength, not extraction.

To verify

Where the 18–22% band came from. The standard origin story credits the Coffee Brewing Center, a US research operation of the 1950s–60s whose brewing curves are said to underpin what is now the SCA Brewing Control Chart. Urnex phrases it as knowing “since the 1950s” through research from the Specialty Coffee Association.³ No source consulted here names the researchers, a founding year, or a primary report title, and the SCA’s own public standards page lists only assessment and equipment-certification standards — it publishes no numeric brewing or extraction values in the open.⁵ Treat the 1950s attribution as trade lore that is probably right rather than as a documented fact.

To verify

The strength half of the “Golden Cup” box. The Brewing Control Chart is usually described as a rectangle: 18–22% extraction on one axis, a strength band on the other. The strength band is where sources part company. Wikipedia lists three different regional standards — American 1.15–1.35%, European 1.20–1.45%, Norwegian 1.30–1.50%¹ — while secondary summaries of the SCA chart quote a single 1.15–1.45%.⁶ This wiki’s Total dissolved solids note flags the same disagreement from other sources. The extraction half of the box is stable; the strength half is not, and anyone quoting one figure as “the SCA standard” is flattening a real regional split.

To verify

Sour equals under-extracted, bitter equals over-extracted. This is the near-universal teaching heuristic, and it is the implied reason 18–22% is called optimal — enough extraction for sweetness and complexity, not so much that you pull harshness.²⁶ It is a practitioner rule of thumb repeated across training material rather than a result traced here to a controlled sensory study, and roast level, water chemistry and the specific coffee all shift where those thresholds land.

Related

• Total dissolved solids — the measurement extraction yield is calculated from, and the strength number people constantly mistake it for
• Brew ratio — the third variable in the same equation
• Coffee grinding — the lever most people reach for first when extraction is off
• Refractometer — the instrument that makes any of this measurable
• Cupping · Coffee scoring — the sensory judgement that a percentage cannot replace
• Specialty Coffee Association — keeper of the standards everyone quotes
• World Brewers Cup — where these numbers get argued about on a stage
• Water for brewing coffee — the other input that changes what comes out of the grounds

Official links

• Official site — Specialty Coffee Association, Coffee Standards

Footnotes

1. Coffee preparation — Wikipedia ↩ ↩² ↩³ ↩⁴

2. Fresh Cup — Coffee Basics: Understanding Extraction Variables ↩ ↩² ↩³ ↩⁴

3. Urnex — Coffee Extraction and the Ideal Brew ↩ ↩²

4. Scott Rao — What are the best dose and brewing ratio? ↩

5. Specialty Coffee Association — Coffee Standards ↩

6. Coffeester — Extraction: Yield & Strength — cited in the research report, not independently fetched ↩ ↩²