Extraction Diagnostic
Tell us what you taste. We’ll tell you what went wrong — and exactly how to fix it for your brew method.
EY% × TDS × SCA
Your coffee is in the sweet spot. The balance of organic acids, sugars, Maillard products, and controlled bitter compounds creates complexity and sweetness. This is the 18–22% extraction yield range where flavor quality peaks.
How This Works
The Extraction Curve
Coffee extraction is sequential. Organic acids dissolve first (they’re small, polar molecules), followed by sugars and Maillard reaction products, then finally the heavier bitter compounds — CGA lactones and phenylindanes. Every cup is a snapshot of how far along this dissolving curve you went. Too little extraction: sour and underdeveloped. Too much: harsh and bitter. The sweet spot lives in the middle.
Acids → Sugars → Bitters
The three stages aren’t equal in volume. Acids make up roughly 10–15% of soluble mass but dissolve earliest and fastest. Sugars and Maillard products represent the bulk of pleasant flavor (40–50%) and come next. Bitter compounds dissolve last — they’re large, complex molecules that need more energy (time, heat, surface area) to extract. The goal is to dissolve enough sugars to balance the acids without pulling significant bitters.
The SCA 18–22% Standard
The Specialty Coffee Association established the 18–22% extraction yield range through decades of sensory research. At this range, trained tasters consistently rate coffee highest for flavor quality. Below 18%, acid compounds dominate and the cup tastes sour or underdeveloped. Above 22%, bitter compounds accumulate faster than flavor complexity increases. The “Gold Cup” standard pairs this with 1.15–1.35% TDS for filter coffee.
Strength vs. Extraction
These are independent variables, which is why this tool uses two sliders. Extraction Yield (EY%) measures what percentage of the coffee’s mass was dissolved — it determines flavor balance (sour vs. bitter). Total Dissolved Solids (TDS%) measures the concentration of those dissolved compounds in your cup — it determines body (thin vs. heavy). You can have high extraction at low strength (bitter and watery) or low extraction at high strength (sour and intense). Fixing your coffee requires identifying which axis is off.
SCA Brewing Standards (2019). Lockhart, E.E. "The Soluble Solids in Beverage Coffee as an Index to Cup Quality" (Coffee Brewing Institute, 1957). Rao, S. "Everything But Espresso" (2010). Hendon, C. et al. "The Role of Dissolved Cations in Coffee Extraction" (Journal of Agricultural and Food Chemistry, 2014). Specialty Coffee Association of America. "Gold Cup" Brewing Standard.