Coffee Brew Ratio Guide — SCA Golden Ratio, Espresso, and TDS Targets
SCA golden ratio: 55g/L (1:18) for drip, TDS 1.15–1.35%. Espresso 1:2 (18g/36g), TDS 8–12%. Cold brew 1:8. Lungo 1:3–4. Brew ratio is the primary lever for beverage strength independent of extraction yield.
| Measure | Value | Unit | Notes |
|---|---|---|---|
| SCA golden ratio | 55 | g coffee per liter of water (1:18) | Established by Lockhart 1957 NRCA research; codified as SCA Brewing Control standard |
| SCA specialty drip TDS target | 1.15–1.35 | % | Measured with a refractometer; center of SCA Brewing Control Chart ideal zone |
| Espresso brew ratio | 1:2 | 18g coffee in / 36g liquid out by weight; SCA specialty standard | |
| Espresso TDS | 8–12 | % | ~8–12x more concentrated than drip coffee |
| Cold brew ratio | 1:8 | 100g coffee to 800ml water; concentrate form before dilution | |
| Lungo ratio | 1:3 to 1:4 | 18g in / 54–72g out; higher extraction yield, more bitter extraction | |
| Ristretto ratio | 1:1 to 1:1.5 | 18g in / 18–27g out; sweetness-forward, lower extraction yield | |
| AeroPress ratio range | 1:6 to 1:18 | Wide range depending on technique; concentrate style at 1:6, light at 1:18 | |
| French press ratio | 1:12 to 1:15 | Coarser than drip, slightly stronger; adjust to taste |
Brew ratio — the mass ratio of dry coffee to water — is the primary lever for controlling beverage strength. It is distinct from extraction yield, which describes the balance of flavor compounds extracted. The SCA’s Brewing Control Chart maps the two-dimensional space of both variables to define the specialty coffee ideal zone.
Brew Ratio Reference
| Method | Brew Ratio | Coffee (g) | Water (ml) | TDS Target |
|---|---|---|---|---|
| SCA drip (golden cup) | 1:18 | 55 | 1000 | 1.15–1.35% |
| Pour-over | 1:15 to 1:17 | 30 | 450–510 | 1.2–1.45% |
| French press | 1:12 to 1:15 | 30 | 360–450 | 1.0–1.4% |
| AeroPress (filter style) | 1:12 to 1:18 | 15–20 | 200–300 | 1.0–1.6% |
| Cold brew concentrate | 1:8 | 100 | 800 | 3–5% (dilute before drinking) |
| Espresso (SCA specialty) | 1:2 | 18 | 36 | 8–12% |
| Ristretto | 1:1 to 1:1.5 | 18 | 18–27 | 10–15% |
| Lungo | 1:3 to 1:4 | 18 | 54–72 | 5–8% |
| Moka pot | 1:7 | 20 | 140 | 3–5% |
| Turkish | 1:10 | 8 | 80 | 2–3% (grounds included in cup) |
The SCA Brewing Control Chart
Developed by Lockhart (1957) and maintained by the SCA, the Brewing Control Chart maps extraction yield (x-axis, 14–26%) against strength/TDS (y-axis, 0.8–1.6% for filter coffee) with an ideal zone at the intersection of 18–22% extraction yield and 1.15–1.35% TDS.
The chart reveals an important insight: the same TDS reading can result from different combinations of ratio and extraction. A too-strong ratio with under-extraction can match TDS of an ideal ratio with proper extraction — but the under-extracted cup will taste sour and hollow despite the same measured strength.
Concentration vs. Extraction: The Key Distinction
| Variable | What it controls | How to adjust |
|---|---|---|
| Brew ratio | Strength (TDS, concentration) | Change coffee dose or water amount |
| Extraction yield | Flavor balance | Adjust grind size, temperature, time, agitation |
| Both in range | SCA ideal zone | Requires both variables to be correct simultaneously |
When a cup tastes weak and sour simultaneously, the ratio is too low AND extraction is too low — adjust both grind (finer) and dose (increase) together. When strong and bitter, reduce dose and grind coarser.
Measuring TDS in Practice
A digital refractometer (e.g., VST Coffee Refractometer, Atago PAL-COFFEE) measures the refractive index of cooled, filtered brew against a water baseline. For accurate readings:
- Use a few drops of coffee — rinse the lens with distilled water between measurements
- Cool sample to room temperature — heat affects refractive index readings
- For espresso, dilute 1:1 with distilled water before measuring, then multiply result by 2
- Average two measurements for reliability
Related Pages
Sources
- SCA Brewing Control Chart and Golden Cup Standard
- Lockhart E (1957) Coffee Brewing Research. NRCA
- SCA Water Activity and Extraction Research
- Rao S (2008) The Professional Barista's Handbook
Frequently Asked Questions
What is the SCA golden ratio and where does it come from?
The SCA golden ratio of 55g of coffee per liter (approximately 1:18 by weight) originates from research by Ernest Lockhart at the MIT-affiliated Coffee Brewing Research Institute in the 1950s, published for the National Restaurant Coffee Association. Lockhart's studies used consumer taste panels to identify the extraction range most people found optimal — work that predates the specialty coffee era but established the baseline for all subsequent SCA brewing standards. The ratio remained largely unchanged in SCA's Brewing Control Chart.
How is brew ratio different from extraction yield?
Brew ratio is the mass ratio of dry coffee to final beverage water — it controls strength (concentration of dissolved solids in the cup). Extraction yield is the percentage of the dry coffee mass that actually dissolved into the water — it controls the balance of flavor compounds extracted. You can have a high ratio (strong coffee) with low extraction yield (sour, underdeveloped) or a low ratio (weak coffee) with high extraction yield (bitter, over-extracted). The SCA ideal zone requires both ratio and extraction yield to be in range simultaneously.
What does TDS measure and how is it used to evaluate brewing?
TDS (total dissolved solids) measures the concentration of dissolved coffee compounds in the final beverage, expressed as a percentage by weight. It is measured with a digital refractometer, which detects how much the solution bends light versus pure water. Combined with brew ratio, TDS allows calculation of extraction yield using the formula: Extraction Yield % = (TDS% × Beverage Weight) / Coffee Dose Weight. Target ranges differ by method: SCA drip 1.15–1.35%, espresso 8–12%.
Should I measure brew ratio by weight or volume?
Weight is strongly preferred in specialty coffee. Volume measurements are unreliable because coffee density varies significantly by grind size, roast level, and bean variety — the same 2 tablespoons can represent 8–14g of coffee depending on these factors. Weight measurement with a scale eliminates this variability and enables consistent, reproducible results. Water should also be measured by weight (1g ≈ 1ml), as volumetric measuring cups are less accurate.