Turn your TDS reading into extraction yield.
Convert a refractometer measurement into the only number that actually tells you whether a cup is dialled in: extraction percentage. Free formula, SCA guidelines, and an iOS app that calculates it for you every brew.
Extraction Yield % = (TDS × Beverage Mass) ÷ Coffee Dose
The Specialty Coffee Association target is 18–22 % extraction. Most great-tasting coffees sit around 19–21 %.
What extraction percentage actually means
Extraction yield is the percentage of the dry coffee grounds that dissolved into your cup. A 20% extraction means 20% of the bean — by mass — ended up as flavor in the beverage. The other 80% stayed in the puck or filter as spent grounds.
Roasters and competition baristas obsess over this number because it is the single most predictive measurement of how a coffee will taste. Two cups with identical dose, time, and ratio can land at very different extractions depending on grind size, water temperature, turbulence, and water chemistry. The taste follows the extraction, not the recipe.
How to calculate extraction yield, step by step
- Weigh the dose. The dry coffee in grams before brewing. A typical espresso dose is 18 g; a typical pour over dose is 15–20 g.
- Weigh the beverage. For espresso, this is the shot weight in the cup. For pour over, weigh the cup of brewed coffee — not the water you started with.
- Take a TDS reading. Cool a small sample to room temperature, drop 2–3 drops onto a calibrated refractometer prism, and read the percentage. Atago, VST, and DiFluid R2 are the common consumer choices.
- Plug into the formula.
Extraction % = (TDS × Beverage Mass) ÷ DoseExample: a 36 g espresso shot at 9.5 % TDS from an 18 g dose = (9.5 × 36) ÷ 18 = 19.0 % extraction. - Compare to the target. 18–22 % is the SCA ideal. Sub-18 % is under-extracted (sour, weak). Above 22 % is over-extracted (bitter, hollow).
Reference: TDS and extraction targets by brew method
| Brew method | Typical TDS | Target extraction |
|---|---|---|
| Espresso (traditional) | 8–12 % | 18–22 % |
| Pour over (V60, Kalita, Origami) | 1.20–1.45 % | 19–22 % |
| AeroPress | 1.30–1.60 % | 19–22 % |
| Batch brew / drip | 1.15–1.35 % | 18–22 % |
| French press (immersion) | 1.20–1.40 % | 18–21 % |
| Cold brew (concentrate) | 1.50–2.50 % | 18–22 % |
Reading the result: what to adjust next
The whole point of measuring extraction is making the next brew better. Here's how to translate a number into an action.
- Under 18 % — under-extracted. The cup tastes sour, weak, and short. Grind finer, raise water temperature, extend contact time, or increase agitation.
- 18–22 % — in the zone. Use taste to fine-tune. Slightly bitter near 22 %? Coarsen one notch. Slightly thin near 18 %? Tighten one notch.
- Over 22 % — over-extracted. The cup tastes harsh, dry, and hollow. Grind coarser, lower temperature, shorten contact time, or reduce agitation.
Why use an app instead of doing the math by hand
You can do extraction math on a calculator. But after a few weeks of dialling in, three things start to matter more than the calculation itself:
- History. The 9.5 % TDS shot you pulled last Tuesday means nothing unless you can find it next to the grind setting, temperature, and tasting notes that produced it.
- Visualisation. A number is a number. Seeing it plotted against the SCA ideal zone — alongside ten previous attempts on the same coffee — is what turns measurement into a feedback loop.
- Coffee-aware context. Extraction targets shift slightly by roast level and process. A washed light roast and a natural dark roast won't taste their best at the same number.
HomeBarista takes your dose, yield, and TDS, drops the result onto a chart with ristretto, optimal, and lungo zones, and links every brew to the bag it came from. The dial-in tool on top adds taste feedback — sour, balanced, bitter — and suggests the next grind move.
Calculate extraction on every brew, automatically.
Free on iOS. Works without a refractometer too (calculates ratio + brew strength estimates).
Frequently asked questions
What is a good extraction percentage for coffee?
The SCA target is 18–22 %. Most cups taste their best around 19–21 %. Below 18 % the cup is weak and sour; above 22 % it turns bitter and harsh.
What is the formula for extraction yield?
Extraction Yield % = (TDS × Beverage Mass) ÷ Coffee Dose. TDS comes from a refractometer, beverage mass is the brewed coffee weight, and dose is the dry grounds you started with.
What TDS should espresso be?
A well-extracted traditional espresso reads 8–12 % TDS. For an 18 g → 36 g shot, around 9–10 % TDS lands inside the SCA 18–22 % extraction target.
What TDS should filter coffee be?
Filter coffee usually targets 1.15–1.45 % TDS. At a 1:16 ratio, around 1.30 % TDS sits near 20 % extraction — the centre of the ideal range.
Do I need a refractometer to dial in coffee?
No. Taste is the final judge. But a refractometer turns guesses into data — it tells you whether a "bitter" cup is genuinely over-extracted or actually under-extracted with high strength, which determines the next adjustment.
How does HomeBarista's extraction calculator work?
Enter dose, yield, and TDS. HomeBarista computes extraction yield, brew ratio, and places the result on a visual chart with ristretto, optimal, and lungo zones. Every calculation is linked to the brew log so you can compare results across attempts.