TDS & Extraction Yield Calculator
Enter your refractometer TDS reading, dose, and beverage mass to get Extraction Yield and see where it falls against the SCA gold-cup range.
Extraction result
The formula behind the number
Extraction Yield is calculated as EY% = TDS% × (beverage mass ÷ dose mass). Take the SCA’s reference example: a 20g dose brewed to 300g of beverage, measuring 1.35% TDS. The brew ratio is 300 ÷ 20 = 15, so EY% = 1.35 × 15 = 20.25% — comfortably inside the 18-22% gold-cup band.
If your reading lands under 18%, the brew pulled less flavor than the reference chart expects for that ratio — try a finer grind, a hotter brew temperature, or a longer contact time. Over 22%, you’ve likely over-extracted — try a coarser grind or a shorter brew.
Frequently Asked Questions
What is TDS and how do I measure it?
TDS (Total Dissolved Solids) is the percentage of your brewed coffee, by weight, that is dissolved coffee solids rather than water. It's measured with a digital refractometer: a drop of brewed (and usually cooled/filtered) coffee gives a direct percentage reading, typically between about 1.0% and 1.5% for filter coffee.
What is Extraction Yield and why does it matter?
Extraction Yield (EY%) estimates what share of the original dry coffee's soluble mass ended up in your cup. It's calculated from TDS and the brew ratio: EY% = TDS% x (beverage mass / dose mass). The SCA's widely used "gold cup" reference places the ideal range at 18-22% for filter coffee — below that tends to taste sour and thin, above it tends to taste bitter and harsh.
My brew is in the 'ideal' band but still tastes bad — why?
The gold-cup chart is a starting reference, not a guarantee. Bean freshness, roast level, water chemistry, and personal taste all shape how a given TDS/EY reading actually tastes. Use the band as a diagnostic starting point, then trust your own palate over the number.
What's the difference between beverage mass and the water I poured in?
Beverage mass is the weight of what actually ended up in your cup or carafe, which is slightly less than the water you poured in because the coffee grounds absorb and retain some water. Weighing the final brewed liquid (not the water added) gives a more accurate Extraction Yield.
A brew-control reference, not a certification standard — use it alongside your own taste, not instead of it.