Extraction Percentage

Extraction percentage (or extraction yield) is the proportion of a coffee's total soluble material that was dissolved into the water during brewing, expressed as a percentage of the dry coffee weight. Coffee grounds contain approximately 28–30% soluble compounds (by weight); the rest is insoluble cellulose fiber. Extraction percentage tells you how much of that soluble material ended up in your cup. The SCA identifies an extraction range of 18–22% as the target for balanced, flavorful coffee.

Under-extraction (below 18%) means not enough soluble material was dissolved. The cup will taste sour, thin, salty, and undeveloped because the pleasant sweet and balancing compounds — which dissolve later in the extraction process — haven't been fully pulled from the grounds. Common causes include too-coarse a grind, insufficient water temperature, or too-short a brew time.

Over-extraction (above 22%) means too much soluble material was dissolved, including the harsh, bitter, astringent compounds that dissolve last. The cup will taste bitter, dry, ashy, and hollow because the unpleasant late-dissolving compounds overwhelm the pleasant ones. Common causes include too-fine a grind, too-hot water, or too-long a brew time.

Extraction percentage is calculated by measuring the TDS (Total Dissolved Solids) of the brewed coffee and using the formula: Extraction % = (Brewed Coffee Weight × TDS) / Dry Coffee Dose. For example, if 18g of coffee produces 300g of brewed coffee at 1.35% TDS, extraction = (300 × 0.0135) / 18 = 22.5%. In practice, most home brewers don't calculate extraction precisely — they adjust grind size, dose, and time based on taste, which is the most practical approach. Understanding the concept of extraction, however, helps diagnose why a cup tastes the way it does.