What is a coffee extraction yield percentage?

Extraction yield percentage (EY%) is the "gold standard" for quantifying how successful a brew has been. While "TDS" (Total Dissolved Solids) measures the strength or concentration of the liquid in your cup, the extraction yield tells you what portion of the original, dry coffee bean ended up in that liquid. It is the ultimate indicator of whether you have extracted the "good" parts of the coffee—the sugars, acids, and aromatics—without pulling out the bitter, woody, or astringent compounds.

In modern specialty coffee, we generally agree that an extraction yield between 18% and 22% produces the most balanced cup. If your yield is below 18%, the coffee is often described as under-extracted, frequently tasting sour, salty, or thin because you have left behind many of the sweet, flavorful compounds. If you exceed 22%, you risk over-extraction, where the coffee becomes bitter, dry, and hollow as the water begins to pull out the undesirable, fibrous material from the grounds.

To calculate this, you need a refractometer to measure the TDS and knowledge of your "brew ratio" (the weight of water used vs. the weight of the coffee grounds). By inputting these numbers into a formula—or a modern brewing app—you get a specific percentage. This allows you to treat coffee brewing like a true science rather than guesswork. If you find your coffee is consistently landing at 17%, you know exactly what to do: increase your extraction by grinding finer, raising your water temperature, or extending your contact time.

While these tools were once reserved for laboratories and competition training, they are increasingly relevant for the serious home brewer. Understanding extraction yield removes the frustration of "hit or miss" brewing. It gives you a clear target to aim for, allowing you to replicate your favorite cup of coffee every single morning. It transforms your daily routine from a guessing game into a repeatable, high-quality craft that you can calibrate to your exact preference.