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 — and 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