When you brew coffee, you are using hot water to extract and dissolve actual coffee out of the grounds. Extraction describes how much of the coffee you’re brewing ends up in your cup. If your extraction is 20%, that means 1/5 of the grounds you were brewing ended up in the water.
Taste testing conducted in the 1950s showed that humans prefer the taste of 18-22% extraction. Less than 18% and the coffee is “under-extracted,” and usually tastes weak, watery, or unbalanced. More than 22% extraction results in distinctly bitter coffee that is considered “over-extracted.”
Questions? Fire them off to firstname.lastname@example.org.