Extraction yield is the share of the dry coffee that ended up dissolved in the cup, expressed as a percentage. It is the number underneath every conversation about sour and bitter.
The window
Roughly 18 to 22 percent is where most coffee tastes good.
Below about 18 percent you have under-extraction: the acids came out, the sugars did not, and the cup is sour, thin and sometimes salty.
Above about 22 percent you have over-extraction: the harsh, dry, woody compounds that dissolve last have joined the party, and the cup is bitter and astringent.
Coffee is only about 30 percent water-soluble at all, so you can never extract everything, and you would not want to.
Measuring it
Properly, with a refractometer: measure the dissolved solids in the brew, multiply by the beverage weight, divide by the dry coffee weight.
At home, taste and time are the practical proxies. That is why we recommend dialing by shot time first and flavor second.
Yield is not strength
This trips people up constantly. Yield is how much dissolved. Strength is how concentrated the result is, which is set by the ratio.
A weak coffee can be perfectly extracted — you simply used more water. A strong coffee can be badly under-extracted. Adding more coffee fixes weakness; grinding finer fixes sourness.
What people want to know
Do I need a refractometer?
No. It is a genuinely useful instrument for someone learning systematically, and it costs several hundred. Time and taste get you to the same place more slowly and for nothing.
Last reviewed 30 October 2026