Extraction Yield and Strength
Two numbers describe almost everything about a brew, and the key insight is that they are independent. Extraction yield (EY%) is how much of the coffee dissolved. Strength (TDS) is how concentrated the resulting liquid is. You can have a strong cup that is under-extracted, or a weak cup that is over-extracted — they are separate axes, and confusing them is the most common conceptual mistake in brewing. 🧭
#Extraction Yield (EY%)
Extraction yield is the percentage of the dry coffee's mass that ended up dissolved in the cup. Brew 20 g of coffee, dissolve 4 g of it, and you have a 20% extraction yield. Of coffee's ~28–30% soluble maximum, most filter brews aim for roughly 18–22%:
- Below ~18% → under-extracted: sour, salty, thin.
- ~18–22% → the commonly cited "sweet spot" for balance.
- Above ~22% → over-extracted: bitter, drying, hollow.
The "18–22%" window came from mid-century research on average American palates and roasts. Modern light roasts and great coffees often taste best above 22%. Let your palate, not the number, draw the lines.
#Strength / TDS
Strength is measured as Total Dissolved Solids — the percentage of the brewed liquid that is dissolved coffee, typically 1.15–1.45% for pour over. Higher TDS tastes more intense and syrupy; lower TDS tastes more delicate and tea-like. Strength is set mainly by the brew ratio (water per gram of coffee), while extraction yield is set mainly by grind, time, and temperature.
#The Relationship 🔗
These three quantities are linked by a simple formula:
Extraction Yield = (Brew Mass × TDS%) ÷ Dose where Brew Mass is the grams of liquid coffee in the cup and Dose is the grams of dry coffee. Measure TDS with a refractometer, weigh your output, and EY falls out.
| You change... | EY moves | TDS moves |
|---|---|---|
| Finer grind | ↑ | ↑ |
| More water (looser ratio) | slight ↑ | ↓ |
| Hotter water | ↑ | ↑ |
| Longer brew time | ↑ | ↑ |
The two axes plotted together create the famous map of brewing space — the Coffee Brewing Control Chart.
#Continue Reading
- Total Dissolved Solids (TDS) — the strength axis in detail
- The Coffee Brewing Control Chart — EY and TDS plotted together
- Refractometers and Measuring Extraction — how to measure both
- The Brew Ratio — the main lever for strength
- Under-Extraction and Over-Extraction — what the EY bands taste like