Turn a TDS reading from your refractometer into an extraction yield percentage — the industry standard measure of how much of the coffee has dissolved into the cup.
EY (%) = TDS (%) × beverage weight (g) ÷ dry dose (g). Enter 1.35 for a 1.35% TDS reading, not 0.0135. Do not multiply by 100 again.
Worked examples: 18 g dry dose, 250 g beverage and 1.35% TDS gives 18.75% EY. An 18 g espresso dose, 36 g yield and 10% TDS gives 20% EY.
The 18–22% band shown is a conventional comparison aid, not an automatic taste verdict or certification. The brew-type selector labels the context; it does not change the mass-balance formula. Follow your refractometer’s coffee-specific sampling, filtering and temperature instructions. Dissolved material retained with grounds is outside this beverage-based estimate; immersion methods need additional assumptions. See SCA’s standards index for the distinction between reference guidance and formal standards.
Yes — this tool depends on a TDS measurement. Palate-based dialling in is fine without one; the refractometer just makes iteration faster.
1.30–1.40% TDS at 20–21% EY is a widely-loved specialty range.
Very long shots (1:3+) and very fine grinds push extraction up. Try shortening the ratio or coarsening slightly.
Refractometer readings drift if the sample is hot or foamy. Cool the sample and eliminate crema before measuring.