EY (Extraction Yield)

Extraction Yield (EY) is the precise measurement of how much of the dry coffee dose ended up dissolved in the cup, expressed as a percentage and calculated with the formula: (brew weight in grams × TDS%) ÷ dry coffee dose in grams × 100. The SCA Gold Cup standard defines optimal filter coffee as achieving 18–22% EY paired with a TDS of 1.15–1.55% (strength), while espresso sits at the same EY range but with a much higher TDS of 8–12% due to its concentrated nature. EY and TDS are complementary metrics: EY tells you how efficiently you extracted the coffee, while TDS tells you how strong the resulting beverage is.

Background & Context

EY (Extraction Yield) is the standardised abbreviation for the percentage of dry coffee mass dissolved during brewing, used in specialty coffee's technical vocabulary to distinguish this measurement from TDS (Total Dissolved Solids, which measures concentration). The SCA Brewing Control Chart — developed by E.E. Lockhart at MIT in the 1950s and refined by the Specialty Coffee Association — defines the "ideal" EY zone as 18–22% for filter brewing. Espresso EY typically targets the same range, though modern light-roast espresso preparation increasingly explores 22–24% through pressure profiling. EY cannot be directly measured without a refractometer; it is derived from the TDS reading, brew weight, and dose weight using the formula: EY(%) = (brew weight × TDS%) ÷ dose weight × 100. Different brewing methods naturally cluster at different EY points within the target range: well-calibrated espresso tends toward 20–22%; V60 tends toward 18–20%.

Practical Use

EY is useful as a calibration benchmark when changing coffees or adjusting recipes. If switching from a Colombian medium roast (calibrated to 20% EY) to an Ethiopian light roast with higher solubility, the same grind setting may produce 22–23% EY — over-extracted despite identical parameters. EY measurement catches this immediately; taste alone might attribute the change to the coffee's inherent character rather than to over-extraction. In professional settings, logging EY alongside TDS for every new lot allows objective comparison of extractability — a useful metric when purchasing green coffee, as more-soluble lots are easier to dial in consistently.

Related Terms

Related terms: TDS, Extraction rate, Brewing control chart, Espresso extraction, Refractometer.