Coffee Extraction Calculator

Extraction yield (EY) is the percentage of the dry coffee grounds' mass that ends up dissolved in your cup: EY% = (TDS% × beverage weight) ÷ dose weight. The SCA considers 18%–22% the "ideal" range for filter coffee — below it, flavor is under-extracted (sour, salty); above it, over-extraction pulls out bitter, astringent compounds.

For filter/drip coffee, the SCA Gold Cup standard targets 1.15%–1.35% TDS — how concentrated the cup tastes, independent of extraction. Espresso runs far higher, typically 8%–12% TDS, because it uses a much smaller ratio of water to coffee.

A two-axis chart — originally from the Coffee Brewing Institute, refined by the SCA — plotting TDS (strength) against extraction yield. It defines an "ideal" box (1.15%–1.35% TDS, 18%–22% extraction) that professional cuppers and competition baristas use to dial in a recipe.

Brew your coffee, let it cool slightly, then place a few drops of the filtered brewed liquid (not grounds) onto a digital refractometer like a VST or Atago. It reads TDS% directly — plug that into this calculator with your dose and beverage weight to get extraction yield.

Strength (TDS%) is how concentrated the cup is. Extraction yield (EY%) is how much of the coffee's total soluble mass you pulled out. You can brew strong-but-under-extracted (too little water) or weak-but-over-extracted (too much water, too long) — they're independent variables, which is exactly what the two-axis chart is designed to separate. See our Brew Ratio Calculator to set dose and water before you brew.

Under-extraction usually comes from grinding too coarse, brewing too fast, water too cool, or too little contact time. Over-extraction usually comes from grinding too fine, brewing too slow, water too hot, or too much agitation. Grind size is the single biggest lever — adjust that first.