Total Dissolved Solids (TDS)
Total Dissolved Solids (TDS) is the share of a brewed coffee's mass that is dissolved coffee rather than water. If a cup is 1.35% TDS, then 1.35% of the liquid's weight is dissolved solids and the remaining 98.65% is water. TDS is the scientific name for what tasters call strength or concentration. It is one of the two numbers, alongside extraction yield, that define any brew. 🔬
Brew TDS (this note) measures dissolved coffee in your cup. Water TDS measures minerals in your brewing water before any coffee touches it. Same acronym, completely different quantity.
#Typical Ranges
| Brew style | Typical TDS | Character |
|---|---|---|
| Delicate pour over | 1.15–1.30% | Light, tea-like, articulate |
| Standard pour over | 1.30–1.45% | Balanced, the common target |
| Strong / immersion | 1.45–1.60% | Heavy, syrupy, intense |
| Espresso (for contrast) | 8–12% | Concentrated shot |
Pour over generally lives around 1.2–1.45%. The SCA's mid-century research centered a "good" cup near 1.15–1.35%, but, as with extraction bands, modern preference often runs higher.
#What Sets TDS 🎚️
Strength is dominated by the brew ratio: how much water you use per gram of coffee. A tight ratio (say 1:15) gives a stronger, higher-TDS cup; a loose one (1:17) a weaker, lower-TDS cup. Because bypass water (water that skirts the bed without extracting) dilutes the brew, dripper geometry and pour style nudge TDS too. Extraction yield also raises TDS (dissolving more coffee puts more solids in the same water), which is why the two numbers, though independent, move together when you change grind or temperature.
#How TDS Is Measured
A digital refractometer shines light through a drop of filtered, cooled brew and reads how much the dissolved solids bend it, reporting TDS as a percentage (or °Brix, converted). It is the only practical way to put a real number on strength; everything else is calibrated tongue.
Your palate's sense of "strong" is also shaped by bitterness, body, and acidity. A high-EY brew can taste intense at a modest TDS, while a clean high-TDS brew can taste surprisingly easy. TDS is the measured strength, not the perceived one.
#Why It Matters
Knowing TDS lets you separate two questions that feel like one: "is this too strong?" (adjust ratio) versus "is this extracted right?" (adjust grind or temperature). That separation is the whole point of the control chart.
#Continue Reading
- Extraction Yield and Strength: the other axis, and how they relate
- Refractometers and Measuring Extraction: putting a number on TDS
- The Coffee Brewing Control Chart: TDS plotted against extraction
- The Brew Ratio: the main dial for strength
- TDS and Mineral Content: the water sense of TDS