How to measure coffee extraction?
Measuring coffee extraction is typically done using a refractometer to determine the (TDS) in your brewed coffee. By combining the TDS percentage with the weight of your coffee and water, you can calculate the Extraction Yield, which tells you exactly how much of the coffee bean's mass was dissolved into your cup.
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For the home enthusiast, measuring extraction is the final frontier of coffee science. While most people brew by taste, professionals use data to ensure consistency and quality. Extraction yield is the percentage of the dry coffee grounds that actually ends up in your liquid coffee. The industry standard for a balanced cup is generally between 18% and 22%. Anything below 18% is considered under-extracted, often tasting sour or salty, while anything above 22% is over-extracted, often tasting bitter or astringent.
To measure this, you need a refractometer, a device that measures the refractive index of your coffee—essentially how much light bends as it passes through the liquid. This measurement gives you the TDS, or the concentration of dissolved solids in the cup. Once you have the TDS, you use a simple formula: (TDS × Brew Weight) ÷ Dry Coffee Weight = Extraction Yield. This calculation gives you a precise, objective number that you can use to adjust your brewing variables.
If your extraction yield is too low, you know you need to increase the extraction. You can do this by grinding finer, increasing the water temperature, or increasing the contact time. If your yield is too high, you do the opposite. This takes the guesswork out of dialing in a new coffee. Instead of making random adjustments, you are making data-driven decisions that lead to a better cup.
While this level of precision is not necessary for everyone, it is an incredible tool for learning. Even if you don't use a refractometer every day, using one for a week can teach you more about how your grinder, water, and technique affect the final cup than months of trial and error. It bridges the gap between the art of brewing and the science of extraction.
In practice, most people will find that their taste buds are their best tool. However, if you find yourself struggling to get a consistent result, or if you are curious about the science behind your morning brew, measuring extraction is a fascinating and rewarding pursuit. It turns the act of brewing into a controlled experiment, allowing you to understand exactly what is happening inside your brewer.
- ·https://sca.coffee/research/coffee-extraction-and-tdsVerify source for reference 1 ↗