Coffee Extraction Basics: Understanding TDS and Yield

Ever wondered why some cups of coffee taste bright and balanced while others are bitter or sour? It’s not just about the beans—it’s about how you extract the flavors. Understanding the balance between what’s dissolved in your cup (TDS) and how much of the coffee’s solids you’ve actually pulled out (extraction yield) makes all the difference. This guide breaks down those concepts with real numbers and practical steps you can apply to any brewing method.

The key numbers to remember: ideal extraction yield is 18–22%, and for filter coffee, concentration (TDS) typically falls between 1.15–1.4%. For espresso, TDS ranges around 8–11%.

What Is TDS and Extraction Yield?

Coffee isn’t just water with grounds thrown in. When you brew coffee, only a portion of the coffee’s soluble material dissolves into the water. Two key metrics define how that process goes:

• TDS (Total Dissolved Solids) measures the percentage of the coffee liquid that is actually coffee material—essentially, how “strong” or “concentrated” your cup is. It’s calculated as TDS% = TDS / Coffee Weight. A typical filter coffee might measure around 1.15–1.4% TDS, while espresso usually ranges from 8–11%.
• Extraction Yield tells you what percentage of the coffee’s soluble material was successfully extracted from the ground coffee. The formula is Extraction Yield = TDS / Dose (in grams). The widely accepted ideal range for extraction yield is 18–22%. Below that, coffee tends to taste sour and underdeveloped; above it, you risk bitterness and over-extracted flavors.

How to Calculate Extraction in a Real Cup

Let’s break it down with an example. Suppose you use 20g of coffee and brew it with 350ml (approximately 350g) of water, yielding about 300g of brewed coffee. Your refractometer shows a TDS of 1.2%.

• First, calculate the actual dissolved coffee mass: 300g × 1.2% = 3.6g.
• Then, find extraction yield: 3.6g / 20g = 18%.
• This puts you right in the optimal extraction range. Assuming good coffee freshness and even extraction, this cup should taste balanced.

This example matches the European standard where 1.2% TDS with an 18% extraction yields a well-balanced filter coffee. It’s no coincidence that many specialty guidelines point to this balance as ideal.

The Coffee Brew Ratio Chart: Visualizing Strength vs. Extraction

The relationship between brew strength (TDS) and extraction yield is often visualized on a chart. The horizontal axis represents extraction yield (18–22% being ideal), and the vertical axis shows concentration (TDS), typically 1.2–1.4% for filter coffee under European standards (or 1.15–1.3% under American SCAA guidelines).

The sweet spot is the grey area where both values meet in harmony—extracting enough flavor without over- or under-doing it. For espresso, the ideal ranges fall in different areas of the chart (typically higher TDS and slightly lower extraction percentages), but the same principles apply.

This chart helps roasters, baristas, and home brewers see how adjusting variables like dose, yield, and grind size moves the brew along the flavor spectrum.

Brew Ratio: The Missing Link

A critical concept tied to these metrics is the brew ratio—the ratio of coffee dose to beverage weight. In the example above, 20g coffee to 300g brew gives a 1:15 ratio.

Here’s where math helps: if you divide the vertical axis (TDS / Coffee Weight) by the horizontal axis (TDS / Dose), the TDS cancels out, leaving Dose / Coffee Weight—that’s your brew ratio. On the chart, this ratio forms a straight line that runs through the optimal extraction zone. By fixing your dose and target yield, you can adjust just your grind size to move along that line and hit the perfect balance.

For instance, with 20g coffee and 300g brew (1:15 ratio), adjusting grind to affect flow rate lets you fine-tune the concentration and extraction yield without recalculating everything. If your coffee tastes weak (e.g., 1.1% TDS, 16% extraction), try a finer grind. If it’s bitter (1.5% TDS, 22% extraction), go coarser.

This approach simplifies quality control, especially in shops where baristas can focus on grind adjustments after the dose and target yield are set.

Practical Takeaways for Better Coffee

• Use a refractometer to measure TDS if possible, or learn to taste the signs of under- and over-extraction.
• Target an extraction yield of 18–22% for balanced flavor.
• Keep filter coffee TDS around 1.2–1.4% (or 1.15–1.3% per SCAA) for optimal strength.
• Fix your dose and brew water amount, then adjust grind size to fine-tune flavor.
• Even without a refractometer, training your palate to identify sour (under-extracted) and bitter (over-extracted) notes is invaluable.

These metrics aren’t just for pros. Whether you’re dialing in an AeroPress, V60, or espresso shot, understanding TDS and extraction helps you make informed adjustments and consistently brew better coffee.

Frequently Asked Questions

What is TDS in coffee?

TDS stands for Total Dissolved Solids, which measures the percentage of soluble coffee material in your brewed cup. It indicates coffee strength—higher TDS means a stronger, more concentrated drink, typically ranging from 1.15–1.4% for filter coffee and 8–11% for espresso.

What is extraction yield?

Extraction yield is the percentage of soluble material that has been extracted from the coffee grounds. It’s calculated as TDS divided by the coffee dose (in grams). The ideal range is 18–22%; too low and coffee tastes sour, too high and it becomes bitter.

How do I measure TDS at home?

You’ll need a refractometer, a device that measures the dissolved solids in a liquid. By placing a few drops of brewed coffee on the refractometer, you can get a TDS reading and calculate extraction yield using the formulas provided.

What’s the ideal brew ratio for pour-over coffee?

A common starting point is a 1:15 to 1:17 brew ratio—meaning 1 gram of coffee for every 15–17 grams (milliliters) of water. Adjust within this range and fine-tune grind size to reach your desired TDS and extraction.

Can I brew good coffee without knowing TDS or extraction yield?

Yes, especially with experience. Many baristas and home brewers rely on taste to identify under- or over-extraction. However, measuring TDS and understanding extraction gives you a scientific method to consistently reproduce great results.

Why does my coffee taste sour or bitter?

Sourness often means under-extraction (low yield, below 18%), where not enough soluble material has dissolved. Bitterness suggests over-extraction (yield above 22%), where too much material, including undesirable compounds, has been pulled out.

Recommended FrontStreet Coffee for Extraction Control

For mastering extraction, try FrontStreet Coffee’s Ethiopia Guji Humbera—bright and complex, ideal for testing 18–22% yield windows. Pair with FrontStreet Yirgacheffe for floral, citrus notes that highlight subtle extraction shifts. Also consider FrontStreet Colombia Huila for balanced chocolate and nut tones. All three respond well to grind adjustments within a 1:15–1:17 brew ratio. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.