Coffee Extraction Math: TDS, Extraction Yield and the Brewing Control Chart
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Coffee extraction yield is the percentage of the dry coffee you used that ended up dissolved in your cup. Brew 20 g of coffee, dissolve 4 g of it into the water, and your extraction yield is 20%. Pair that number with how concentrated the drink is (its TDS, or total dissolved solids) and you can describe almost any cup of coffee with two numbers.
This guide explains both measurements, gives you the formulas, works through real examples, and shows how the classic brewing control chart and newer research help you turn numbers into better-tasting coffee.
Key takeaways
- TDS is strength: the percentage of your drink that is dissolved coffee. Filter coffee is usually around 1.1 to 1.5%; espresso is much higher.
- Extraction yield (EY) is how much of the coffee dose you dissolved: EY = beverage mass × TDS ÷ dose.
- The classic target for filter coffee, set in the 1950s, is 18 to 22% extraction at 1.15 to 1.35% TDS.
- Newer UC Davis research shows people’s preferences are spread over a wide range, so the chart is a starting map, not a rule.
- To change extraction, change grind first; to change strength, change the ratio.
In this article
- Strength vs extraction
- The formulas
- Worked examples
- The brewing control chart
- What under- and over-extraction taste like
- Measuring TDS with a refractometer
- How to adjust your brew
- FAQ
Strength vs extraction: two different questions
People often mix up “strong” and “well extracted,” but they answer different questions.
- Strength (TDS) asks: how concentrated is the drink in my cup? A TDS of 1.3% means that 100 g of coffee beverage contains 1.3 g of dissolved coffee and 98.7 g of water.
- Extraction (EY) asks: how much did I pull out of the grounds? Roasted coffee is mostly insoluble plant material. Only part of it can dissolve, and the part you dissolve changes the flavor balance.
You can have a strong but under-extracted cup (lots of coffee, coarse grind, short brew) or a weak but over-extracted one (too little coffee, very fine grind, long brew). That is why you need both numbers.
The formulas
Brew ratio
Ratio = water ÷ coffee dose. 60 g of coffee per 1,000 g of water is 1:16.7.
Extraction yield (percolation: drip, pour-over, espresso)
EY (%) = beverage mass (g) × TDS (%) ÷ dose (g)
Weigh the coffee that actually ended up in the cup or carafe, not the water you poured. Some water always stays trapped in the wet grounds.
Extraction yield (immersion: French press, cupping, cold brew)
In immersion brewing, the liquid left in the grounds has the same concentration as the liquid you pour off, so the dissolved solids are spread through all the water you used. A more accurate formula is:
EY (%) = TDS × water mass ÷ ((1 − TDS) × dose), with TDS written as a decimal (1.3% = 0.013).
Using the percolation formula for immersion will underestimate your extraction, as the example below shows.
Predicting TDS before you brew
Rearranging the first formula: TDS = EY × dose ÷ beverage mass. As a rule of thumb, ground coffee holds back roughly twice its weight in water, so beverage mass ≈ water − 2 × dose for filter brewing.
Worked examples
Example 1: pour-over
- Dose: 20 g coffee. Water: 320 g (1:16).
- Beverage in the server: 280 g. Refractometer reading: 1.35% TDS.
- EY = 280 × 1.35 ÷ 20 = 18.9%.
That sits inside the classic 18 to 22% window and right at the top of the classic strength range.
Example 2: the same recipe, but sour
- Same 20 g dose and 280 g beverage, but TDS reads 1.15%.
- EY = 280 × 1.15 ÷ 20 = 16.1%.
Under-extracted. The cup will likely taste sour and thin. Grind finer and brew again.
Example 3: espresso
- Dose: 18 g. Shot weight: 36 g (a 1:2 ratio). TDS: 9%.
- EY = 36 × 9 ÷ 18 = 18.0%.
Espresso uses the same extraction math, just at a much higher strength. Add 150 g of hot water to make an Americano and TDS drops to about 1.7% (3.24 g of dissolved coffee in 186 g), but extraction stays 18% because you did not dissolve anything new.
Example 4: French press (immersion)
- Dose: 30 g. Water: 500 g. TDS: 1.30%. You pour off about 440 g.
- Immersion formula: EY = 0.013 × 500 ÷ (0.987 × 30) ≈ 22.0%.
- Percolation formula with the 440 g you poured: 440 × 1.30 ÷ 30 ≈ 19.1%, an underestimate of about 3 points.
Example 5: planning a batch brew
You want about 20% extraction from 60 g of coffee and 1,000 g of water. Beverage ≈ 1,000 − 120 = 880 g, so TDS ≈ 20 × 60 ÷ 880 ≈ 1.36%. If that is stronger than you like, use a little more water rather than grinding coarser.
| Example | Dose | Beverage or water | TDS | EY |
|---|---|---|---|---|
| Pour-over, balanced | 20 g | 280 g beverage | 1.35% | 18.9% |
| Pour-over, sour | 20 g | 280 g beverage | 1.15% | 16.1% |
| Espresso 1:2 | 18 g | 36 g beverage | 9% | 18.0% |
| French press | 30 g | 500 g water | 1.30% | 22.0% |
| Batch brew plan | 60 g | 880 g beverage (est.) | 1.36% (predicted) | 20% (target) |
The brewing control chart
The classic chart
The brewing control chart plots strength (TDS) on one axis and extraction yield on the other, with diagonal lines for brew ratios. It goes back to Ernest E. Lockhart, a biochemist who led the Coffee Brewing Institute in the United States and published his work on soluble solids and cup quality in 1957. The chart’s famous center box marks 18 to 22% extraction and 1.15 to 1.35% TDS for filter coffee. Around it are eight zones labeled with combinations such as “strong under-developed” or “weak bitter.”
What newer research adds
The UC Davis Coffee Center, with support from the Specialty Coffee Association, spent years testing brews across the chart with trained tasting panels and everyday coffee drinkers. One of their studies, published in the Journal of Food Science in 2021, asked 118 consumers to taste 27 coffees and concluded, as its title says, that preferences for black coffee are spread over a wide range of brew strengths and extraction yields. The resulting Sensory and Consumer Brewing Control Chart links positions on the chart to flavor descriptions rather than to one “correct” box.
The practical lesson: the classic window is a sensible starting point, especially for clean, balanced filter coffee, but your own preference may sit outside it, and that is fine.
What under- and over-extraction taste like
| Extraction | Typical taste | Usual cause |
|---|---|---|
| Under (below about 18%) | Sour, salty, thin, short finish | Grind too coarse, water too cool, brew too short |
| Balanced (about 18 to 22%) | Sweet, clear acidity, lingering finish | Grind, time and temperature in harmony |
| Over (above about 22%) | Bitter, harsh, dry or hollow aftertaste | Grind too fine, brew too long, uneven flow |
Different compounds dissolve at different speeds. Acids tend to come out early, sugars and browning-reaction products follow, and heavier bitter compounds dominate late. Stopping too early leaves the sweetness behind; going too far adds bitterness and astringency.
Measuring TDS with a refractometer
A coffee refractometer measures how much a sample bends light (its refractive index) and converts that to TDS. Tips for accurate readings:
- Cool the sample to room temperature, or use a model that compensates for temperature.
- Zero the device with the same water you brew with.
- Stir before sampling. The first and last drops of a brew are different strengths.
- Filter espresso samples (many people use syringe filters) because undissolved fines can skew the reading.
- Take two or three readings and average them.
No refractometer? You can still use the math. Keep your ratio fixed, change one variable at a time, and let taste tell you which direction to go.
How to adjust your brew
| Your result | Change this | Keep this the same |
|---|---|---|
| Sour, EY too low | Grind finer, or use hotter water | Ratio |
| Bitter and dry, EY too high | Grind coarser, shorten the brew | Ratio |
| Balanced but too weak | Use more coffee (lower ratio, e.g. 1:15) | Grind |
| Balanced but too strong | Use more water (higher ratio, e.g. 1:17), or add water after brewing | Grind |
Freshness matters too. Very old coffee extracts unevenly and loses aroma whatever the numbers say; our guide to fresh roasted vs supermarket coffee explains why, and whole bean vs ground coffee covers grinding at home.
Coffees to practice with
Single origins are ideal for dialing in, because you taste one coffee’s character clearly as you move around the chart. Our Brazil Santos, a low-acidity medium roast with cocoa and nutty notes, is forgiving while you learn. Our Papua New Guinea, a fully washed coffee with caramel, honey and fruit notes, rewards a careful, balanced extraction. Explore all our single origins, each roasted 1–5 days before delivery.
Coffee extraction FAQ
What is a good extraction yield for coffee?
The classic target for filter coffee is 18 to 22%. Espresso is often in a similar or slightly wider range. Treat it as a starting point and adjust to taste.
What TDS should espresso have?
Espresso is far stronger than filter coffee, commonly somewhere around 8 to 12% TDS depending on the ratio and style. A ristretto will read higher and a lungo lower.
Can you calculate extraction without a refractometer?
Not precisely, because you need TDS. You can estimate it by drying the brewed coffee and weighing the solids, but for home use, taste plus consistent recipes works well.
Does a longer brew always mean higher extraction?
Generally yes, if nothing else changes, but the effect slows over time. Grind size usually has a bigger effect than time alone.
Why does my French press math look wrong?
Probably because you used the percolation formula. In immersion brewing, use the water mass and the immersion formula, or you will underestimate extraction by a few points.
Sources
- Fionn Pooler, “Why the New Coffee Brewing Control Chart is a Big Deal,” Fresh Cup, 2024. freshcup.com
- Cotter A.R., Ristenpart W.D., Guinard J.-X., “Consumer Preferences for Black Coffee are Spread Over a Wide Range of Brew Strengths and Extraction Yields,” Journal of Food Science, 2021 (dataset on Dryad). datadryad.org
- “Publications,” UC Davis Coffee Center. coffeecenter.ucdavis.edu
Facts checked in October 2026.
Keep reading: How to make espresso at home · Single origin vs blend coffee · Single origins collection