Once you have a refractometer, cupping stops being purely sensory. You can measure the actual concentration of the brew (TDS, total dissolved solids) and use that to back-calculate the extraction yield. The Barista Hustle protocol is the most-cited standard for this — it targets 1.4% TDS at 8 minutes after pour, with a fixed 11 g / 200 ml ratio.
Why measure TDS at all
Sensory cupping is excellent at detecting direction (sour, sweet, balanced, bitter) but bad at detecting magnitude. Two coffees that taste "balanced" can be at different extraction yields. A refractometer gives you a number. Combined with the brew ratio, that number tells you what percentage of the coffee solubles actually made it into the cup. That's the extraction yield.
A standard cupping bowl with 1.4% TDS at 11:200 corresponds to roughly 22% extraction yield — which sits in the SCA "ideal" extraction band of 18–22%. Below that and the cup is sour and underdeveloped. Above and it tips into bitter and dry.
The Barista Hustle target, in numbers
- Dose: 11 g per bowl. Accurate to ±0.1 g.
- Water: 200 g, just off a rolling boil. Filtered, neutral mineralisation (~70 ppm hardness, pH 7.0–7.4).
- Grind: aim for whatever grind hits 1.4% TDS at 8 minutes for your equipment and coffee. Start medium-coarse (US #20 sieve, ~850 µm) and adjust by trial.
- Bowls: 2–6 per sample. Every bowl within ±2 g of water mass.
- Steep: pour fast, fill to rim, leave 4 minutes, break, skim, wait until 8:00, then sample.
How to measure
- After breaking and skimming, wait until the cup cools to drinkable temperature (~70 °C is fine for most refractometers — check yours; some require lower).
- Pull a small sample with a syringe or pipette. The sample should be from the body of the brew, not the surface.
- Filter the sample through a paper filter (a small AeroPress disc or a folded paper cone works) to remove fines that throw off the reading.
- Drop two to three drops on the refractometer. Read.
Most brewing refractometers report TDS as a percentage. A reading of 1.4 means 1.4 g of dissolved solids per 100 g of brew — your target.
Reading what the number means
- Below 1.3%: under-extracted. Tighten the grind one notch and re-cup. The cup will likely taste sour or thin to match.
- 1.3–1.5%: in the band. Sensory evaluation is now meaningful. Differences across coffees at the same TDS are bean differences, not extraction differences.
- Above 1.5%: over-extracted. Coarsen the grind. The cup will likely taste hollow, papery, or bitter.
When the target is wrong
The 1.4% target is a calibration guide, not a recipe for "good." Some coffees taste best at lower TDS (delicate florals can lose definition above 1.3%). Some dark roasts taste best a touch under (a 1.2% dark roast can be sweeter than a 1.4% one). The target is a starting point — find your coffee's sweet spot empirically.
What the target does give you is consistency. If you're cupping the same coffee across days or grinders, hitting 1.4% each time means any sensory difference is real, not extraction noise. Without the refractometer, that signal is lost in a fog of variation.
When you don't need it
Most home cupping doesn't need a refractometer. If you're comparing two coffees side by side at the same dose, water, and grind, the relative differences are honest even if the absolute extraction is off. The refractometer matters most when you're cupping the same coffee across sessions — it's the only way to know whether the brew, not the coffee, has shifted.