Coffee TDS and Coffee Extraction
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Lets take an example, Understanding Espresso TDS & Extraction (18g Dose → 40g Yield)
Why this matters
In espresso, two numbers explain most of what you taste:
- TDS (Total Dissolved Solids) = strength (how concentrated the espresso is)
- Extraction Yield (EY%) = efficiency (how much of the dry coffee you dissolved into the cup)
You can pull the same recipe and still get very different results depending on TDS and extraction.
Your recipe (fixed inputs)
- Dose: 18 g ground coffee
- Yield: 40 g espresso (measured on a scale)
- Brew ratio: 18 g in → 40 g out = 1:2.22
Step 1: What is TDS in espresso?
TDS is the percentage of dissolved coffee material in the beverage.
- Example: 9% TDS means ~9 g of dissolved coffee solids per 100 g of espresso.
- Espresso commonly sits around 8–12% TDS (varies by style and recipe).
TDS is measured using a coffee refractometer.
Step 2: What is extraction yield (EY%)?
Extraction yield tells you what fraction of the dry coffee dose ended up dissolved in the cup.
Working formula:
EY% = (Beverage mass × TDS) ÷ Dose × 100
- Beverage mass = espresso yield in grams (here, 40 g)
- TDS = decimal form (e.g., 9% → 0.09)
- Dose = dry coffee in grams (here, 18 g)
Worked examples (18 g in, 40 g out)
The table below shows realistic espresso TDS readings and what they mean for dissolved solids and extraction yield.
| TDS (%) | TDS (decimal) | Beverage mass (g) | Dissolved solids (g) = 40 × TDS | EY (%) = (40 × TDS ÷ 18) × 100 | Typical taste direction (if extraction is even) |
|---|---|---|---|---|---|
| 8.0% | 0.08 | 40 | 3.2 g | 17.8% | Can taste sharp/sour, hollow (often under-extracted) |
| 9.0% | 0.09 | 40 | 3.6 g | 20.0% | Often balanced, sweet, syrupy (common “target zone”) |
| 10.0% | 0.10 | 40 | 4.0 g | 22.2% | Heavier body; may turn bitter/drying if too high or uneven |
The key takeaway (same recipe, different results)
With 18 g dose and 40 g yield, your ratio is fixed—but TDS can still change due to:
- Grind size and grind uniformity
- Shot time and flow rate
- Distribution and tamping
- Basket choice and puck depth
- Water temperature and pressure
Because EY% depends on TDS, extraction changes too.
Quick taste map (practical)
- Low EY (often < ~18–19%): sour/sharp, thin, hollow
- Mid EY (often ~19–22%): sweeter, more balanced, syrupy
- High EY (often > ~22%): bitter/harsh, drying/astringent
Note: If a shot tastes both sour and bitter, it’s often uneven extraction (channeling)—even if the numbers look “normal.”
Bottom line for baristas: Lock your recipe (18g in → 40g out), then chase even extraction first (good distribution, level tamp, no channeling).
Use TDS to confirm strength and EY% to confirm how much you extracted—aim for a sweet, balanced cup (often ~9–10% TDS and ~19–22% EY).
If it’s sour, push extraction (slightly finer grind / a bit longer time);
if it’s bitter/drying, reduce extraction (slightly coarser grind / a bit shorter time) while keeping the shot flowing evenly.