Glossary

Beverage & Wine

Brew Ratio & TDS

Also: coffee-to-water ratio, total dissolved solids, brew strength, extraction strength

The coffee-to-water ratio defines how much coffee is brewed relative to water; TDS measures the concentration of dissolved solids in the finished cup, together controlling both strength and extraction yield.

The concept of a coffee brewing control chart was formalized by Earle Lockhart at MIT in 1957 for the Pan-American Coffee Bureau; TDS measurement via refractometer entered specialty practice in the 2000s.

Definition

Brew ratio is the mass relationship between dry coffee grounds and brew water, almost always expressed as 1:X (e.g., 1:15 means 1 gram of coffee per 15 grams of water). It is the primary lever for controlling coffee strength — how concentrated or dilute a cup tastes. The Specialty Coffee Association's Golden Cup standard targets a brew ratio of roughly 1:16 to 1:17 for filter coffee (55–65 grams per litre), though espresso sits at the opposite extreme, typically 1:2 to 1:2.5 (a 'normale' or 'lungo' shot). Total Dissolved Solids (TDS) is the measurable outcome: the percentage of dissolved coffee material in the final liquid, typically 1.15–1.45% for a well-brewed filter coffee and 7–12% for espresso. TDS is measured with a refractometer. Brew ratio and TDS are related but distinct: two cups can share the same TDS but different extraction yields if one is brewed from a higher dose at lower extraction. The 'Specialty Coffee Brewing Control Chart' (derived from Lockhart's 1950s work) plots TDS against extraction yield, carving out an 'Ideal' rectangle where most palates find balance. Ratios outside those bounds shift the cup toward under-strength (sour, watery) or over-strength (bitter, syrupy) regardless of extraction accuracy. Espresso ratios also encode 'Beverage Weight': the shot's output mass relative to the dose, now commonly tracked digitally on scales beneath the portafilter.

In use

“She brewed at a 1:14 ratio for a denser, syrupy cup, then checked the TDS with a refractometer — 1.52%, a touch high, so she dialled back the dose by two grams.”

See also

Related terms

Extraction (Coffee)RefractometerGolden Cup StandardDoseYieldBeverage WeightContact Time

References

  1. 1.The Coffee Brewing Handbook — Ted Lingle (SCAA, 1996)
  2. 2.The World Atlas of Coffee — James Hoffmann (Mitchell Beazley, 2014)
  3. 3.Modulating the Flavor Profile of Coffee — Flament & Bessière (2002)
  4. 4.SCA Brew Ratio & Extraction Resources — Specialty Coffee Association (2018)

Confidence: high

Notes

Ratio vs. Strength vs. Extraction

Strength (TDS) and extraction yield are often conflated but describe different things. Strength is how concentrated the cup is — a function of ratio. Extraction yield is how much of the coffee's soluble mass ended up in the cup — a function of grind, temperature, and time. A cup can be strong but under-extracted (high dose, coarse grind, short brew) or weak but over-extracted (low dose, fine grind, long brew). The SCA Brewing Control Chart maps both axes simultaneously.

Espresso Ratio Conventions

In espresso, the brew ratio is often called the 'Beverage Weight Ratio' or simply 'ratio' and is tracked as dose-in to liquid-out. A 1:2 ratio from a 18 g dose yields a 36 g shot. Third-wave cafés commonly record ratios as '18 in / 36 out' or use notation like '1:2' or '1:2.5' for a lungo. Ristretto shots run ≤ 1:1.5; lungos exceed 1:3.