Measuring what ends up in the cup
Coffee beans are about 30% soluble, but you only want to extract part of that. Extract too little and the coffee tastes sour and thin; extract too much and it turns bitter and dry. Extraction yield puts a number on this balance and lets you adjust the grind, the time or the ratio with intent rather than by guesswork.
The formula
Extraction yield = TDS × beverage weight ÷ dose
- TDS (total dissolved solids) is the strength of the drink in percent, read with a coffee refractometer.
- Beverage weight is the weight of the coffee in the cup, in grams.
- Dose is the weight of dry ground coffee, in grams.
Example: espresso
18 g of coffee yields 36 g of espresso with a TDS of 9.5%:
- Dissolved coffee = 9.5% × 36 = 3.42 g
- Extraction yield = 3.42 ÷ 18 = 19%
- Brew ratio = 1:2
Example: pour-over
20 g of coffee brewed with 320 g of water gives about 280 g in the carafe, since the grounds hold about 40 g. With a TDS of 1.35%:
Extraction yield = 1.35 × 280 ÷ 20 = 18.9%
Target ranges
| Measure | Usual range |
|---|---|
| Extraction yield | 18 to 22% |
| Filter coffee TDS | 1.15 to 1.45% |
| Espresso TDS | 8 to 12% |
The 18–22% window comes from brewing research led in the United States in the 1950s and later adopted by the Specialty Coffee Association. Treat it as a starting point: many light roasts taste best around 20–22%, and darker roasts often below 20%.
How to adjust
- Extraction too low: grind finer, brew longer, use hotter water or a higher ratio of water to coffee.
- Extraction too high: grind coarser, shorten the brew or lower the water temperature.
- Strength wrong but extraction fine: change the ratio of coffee to water without changing the grind.
Measuring TDS properly
Stir the coffee, take a small sample, let it cool to room temperature, then read it on the refractometer. Many baristas filter espresso samples with a syringe filter to remove fine particles that would distort the reading.