Coffee Extraction Explained: Key Terms and Methods

Ever wonder why your pour-over tastes weak while your espresso feels harsh? It’s not just about beans or roast—it’s about what actually ends up in your cup. Only 30% of a coffee bean is soluble, and not all of it tastes good. Getting the right balance of extracted solids and overall concentration is what separates a balanced cup from a disappointing one.

The key numbers? Specialty coffee aims for a TDS (total dissolved solids) between 1.15%–1.35% (SCAA) or 1.2%–1.45% (SCAE), with an extraction yield typically between 18%–22%. But how do you measure that? Let’s break it down.

What Is Coffee Concentration and Why Does It Matter?

Only 30% of a coffee bean can dissolve in water, and within that 30%, there are both desirable aromatic and flavour compounds—and some undesirable ones. Simply extracting more doesn’t guarantee better taste. In fact, over-extraction can bring out bitterness, while under-extraction leaves sourness. That’s why concentration—how much dissolved coffee is in your brewed liquid—is a critical factor alongside extraction yield.

How to Measure Coffee Concentration (TDS)

There are three common ways to measure the concentration of dissolved solids in your coffee, all providing a TDS (total dissolved solids) percentage:

1. Refractometer (e.g., VST Refractometer)

This tool measures how light bends (refracts) when it passes through your coffee. The device converts that refraction data into a TDS percentage. For example, water might read 0.1%, while a typical coffee might show around 1.3% TDS (often rounded to 1.2% for ease).

2. Conductivity Pen (TDS Meter)

This tool measures the electrical conductivity of the coffee, which comes mostly from dissolved electrolytes. Since electrolytes make up roughly 10% of the total dissolved solids, the meter’s raw reading (in ppm) is converted to estimate TDS. For instance, water may read 100ppm, while coffee might read 1300ppm—but the actual TDS is closer to 1200ppm, or 1.2%.

3. Evaporation/Drying Method

The most accurate but labor-intensive method: weigh the coffee liquid, evaporate all the water, then weigh the remaining dry solids. Divide that by the original brew weight to get the true concentration. This method is highly accurate but requires controlled drying conditions.

These tools help you understand how much coffee material you’ve actually dissolved into your cup—essential for consistency and quality.

Understanding TDS and PPM

• TDS is expressed as a percentage (%); common specialty coffee TDS targets are 1.15%–1.35% (SCAA) or 1.2%–1.45% (SCAE).
• PPM means “parts per million” and is often used interchangeably with TDS in conductivity tools. 1ppm = 1mg of solute per kg (or L) of solution. So 1200ppm = 0.12% TDS.

How to Calculate Extraction Yield

Extraction yield tells you what percentage of the coffee bean’s soluble material you’ve actually pulled into the cup. You calculate it using one of these methods:

• (Refractometer or Conductivity TDS reading × Total brew weight) ÷ Weight of dry coffee grounds
• (Weight of dried coffee solids ÷ Weight of dry coffee grounds)

Note: The drying method is the most accurate, but it demands lab-like conditions. Other methods ignore variables like coffee’s water absorption during brewing.

Brew Method-Specific Extraction Calculations

To tailor your calculations to how you actually brew, use these formulas based on brew type:

1. Immersion Methods (e.g., French Press, Clever Dripper, Cupping)

Formula: (Brew Water Weight × TDS%) ÷ Coffee Grounds Weight
Example: (240g water × 1.2%) ÷ 15g coffee = 19.2% extraction

2. Drip/Filter Methods (e.g., Pour Over, Chemex, AeroPress, French Press with drainage)

Option 1: (Final Coffee Liquid Weight × TDS%) ÷ Coffee Grounds Weight
Example: (240g coffee liquid × 1.2%) ÷ 15g coffee = 19.2%

Option 2: [(Brew Water Weight − Coffee Absorption) × TDS%] ÷ Coffee Grounds Weight
Note: Coffee typically absorbs ~2× its weight in water (e.g., 15g coffee absorbs ~30g water).
Example: [(280g water − 30g absorbed) × 1.2%] ÷ 15g = 20% extraction

3. Espresso

Before measuring TDS, filter out any suspended solids (use the VST filter or substitute with regular filter paper).
Formula: (Espresso Liquid Weight × TDS%) ÷ Coffee Grounds Weight
Example: (36g espresso × 10%) ÷ 18g coffee = 20% extraction

Frequently Asked Questions

What is TDS in coffee?

TDS stands for Total Dissolved Solids, and it measures the percentage of soluble coffee material in your brewed cup, usually between 1.15%–1.35% for optimal flavour according to SCAA guidelines.

What is a good extraction yield percentage?

Specialty coffee typically aims for an extraction yield of around 18%–22%. This means 18%–22% of the coffee bean’s soluble material has been extracted into the brew.

How do I measure coffee concentration at home?

You can use a VST refractometer for the most accurate TDS percentage, or a conductivity (TDS) pen that estimates TDS based on conductivity (usually needs a ppm-to-percentage conversion).

What’s the difference between TDS and extraction yield?

TDS measures how much soluble coffee is in your final brew (as a %), while extraction yield measures what percentage of the original coffee bean’s soluble material was successfully extracted.

Which brew method needs the most precise TDS measurement?

All methods benefit from TDS measurement, but espresso and immersion brews like French press can vary greatly, so measuring TDS helps achieve consistency, especially in competition or specialty settings.

Do different brew methods affect how I calculate extraction?

Yes. Immersion, drip, and espresso each have specific formulas due to differences in water contact time, absorption, and drainage, which must be factored into accurate yield calculations.

Recommended FrontStreet Coffee for Extraction Experiments

Try FrontStreet Coffee’s Ethiopia Humbera for bright, complex fruit and floral notes, ideal for practising pour-over techniques. Their Yirgacheffe offers citrus and jasmine brightness, great for dialling in drip methods. For espresso, their Classic Blend delivers balanced chocolate and nuttiness—perfect for testing TDS and extraction in milk drinks. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.