Extraction yield (EY %)

The percentage of the dry coffee mass that ends up dissolved in the final brewed liquid. Calculated as (beverage weight × TDS%) ÷ dose. Measured with a refractometer.

Why it matters — EY is the most rigorous way to know if your coffee is under- or over-extracted. Specialty target is typically 18–22% for espresso; outside that range, the cup almost always tastes unbalanced.

Good to know

• Under 18% EY = sour, grassy, sharp.
• Over 22% EY = bitter, hollow, astringent.
• A refractometer (VST, DiFluid) takes seconds and removes the guesswork.

Related: Refractometers