How to Calculate Coffee Extraction Rate and TDS

Ever wonder why the same single origin coffee can taste radically different — sometimes thin and underwhelming, other times rich but bitter? The difference often comes down to two numbers: extraction rate and TDS (total dissolved solids). These metrics define how much flavor you’re pulling from the coffee grounds, and how concentrated that flavor ends up in your cup.

Here’s the quick answer: Specialty coffee aims for a 20% extraction rate and 1.1–1.3% TDS. Lower extraction (like 15%) paired with higher TDS (1.3–1.6%) yields a strong but simpler cup; hitting 20% extraction with 1.2% TDS brings out more layered flavors, though it may taste lighter.

What Is Coffee Extraction Rate?

Coffee extraction rate refers to the percentage of soluble material pulled from ground coffee during brewing. Not all compounds in coffee are desirable — getting the right amount out is what creates balance. The basic formulas are:

• Coffee concentration = weight of extracted solids ÷ weight of brewed coffee liquid
• Extraction rate = weight of extracted solids ÷ weight of coffee grounds used

Put simply, extraction rate tells you what portion of the coffee bean’s soluble material you’ve actually brewed into the cup.

The Science Behind Extraction and TDS

Two key values determine your coffee’s profile:

• Extraction Rate (Extract Rate): Measures how much of the coffee’s soluble material (in grams) you’ve extracted from the coffee grounds (also in grams), expressed as a percentage. For example, extracting 20g of solids from 100g of coffee grounds gives you a 20% extraction rate.
• TDS (Total Dissolved Solids): Measures the concentration of those extracted solids in your final brewed coffee (in grams per gram of liquid), also as a percentage. A TDS of 1.3% means 1.3% of your brewed coffee is solid compounds.

According to both the SCA (Specialty Coffee Association of America) and the SCAE (now part of the SCA), the ideal “Gold Cup” standard sits at 20% extraction rate with a TDS between 1.1% and 1.3%. This range is widely regarded as the sweet spot for balanced flavor: enough extraction to develop complexity, not so much as to introduce unpleasant notes.

Real-World Examples from FrontStreet Coffee

At mojo, a busy single-origin bar setup led to a streamlined but less precise brewing process. To save time and avoid under-extracted bitterness, the shop used a method with high coffee dose, fine grind, and shorter brew time. This resulted in a lower extraction rate (around 15%) but higher TDS (1.3–1.6%). The trade-off? A stronger, richer cup that minimized harsh or sour flavors, though at the cost of some nuance.

Four years later, retro — equipped with a Clover brewer for precise temperature and time control — aimed for the Gold Cup standard. Here, baristas targeted 20% extraction with around 1.2% TDS. The result was a more aromatic, layered cup with greater clarity and complexity. However, the slightly lower TDS meant some customers perceived it as thinner compared to mojo’s style.

Both approaches illustrate how extraction rate and TDS influence not just numbers, but actual taste: body, balance, brightness, and finish.

How to Apply These Numbers in Brewing

If you’re dialing in your pour-over, espresso, or batch brew, here’s what to keep in mind:

• Too low extraction (<18–19%)? Your coffee may taste sour, grassy, or under-developed.
• Too high extraction (>22%)? Expect bitter, astringent, or drying notes.
• TDS too low (<1.0%)? Your coffee will taste weak or watery.
• TDS too high (>1.4–1.5%)? Expect excessive strength or muted flavors.

Most home and shop brewers don’t measure TDS or extraction rate directly — but tools like refractometers (and software like Extract Mojo) let professionals dial these in. Even without lab gear, understanding these principles helps guide grind size, brew time, water amount, and coffee dose.

Frequently Asked Questions

What is coffee extraction rate?

Coffee extraction rate is the percentage of soluble solids extracted from coffee grounds during brewing. It’s calculated by dividing the weight of extracted material by the weight of the original coffee grounds, then multiplying by 100. For example, extracting 20 grams of solids from 100 grams of coffee equals a 20% extraction rate.

What is TDS in coffee?

TDS stands for Total Dissolved Solids, the percentage of soluble coffee material present in the brewed liquid. It’s calculated by dividing the weight of dissolved coffee solids by the total weight of brewed coffee, then multiplying by 100. A typical TDS for specialty coffee ranges between 1.1% and 1.3%.

What is the ideal extraction rate and TDS for specialty coffee?

The Specialty Coffee Association’s “Gold Cup” standard recommends a 20% extraction rate and a TDS between 1.1% and 1.3%. This balance is considered ideal for a complex yet smooth cup.

Why did mojo use lower extraction and higher TDS?

Due to time constraints in a busy single-origin service, mojo used high coffee dose, fine grind, and short brew times. This resulted in about 15% extraction and 1.3–1.6% TDS — a stronger, richer cup that avoided under-extraction but sacrificed some subtlety.

Why does retro aim for 20% extraction and 1.2% TDS?

With a Clover brewer offering precise control, retro targeted the Gold Cup standard — 20% extraction and around 1.2% TDS. This approach highlights more layered flavors and aroma, though the slightly lower TDS can make the cup taste lighter.

Recommended FrontStreet Beans for Extraction Experiments

Try FrontStreet’s Ethiopia Humbera for bright, layered profiles that respond well to 20% extraction; its citrus and floral notes shine at Gold Cup TDS levels. For deeper complexity, their Yirgacheffe offers berry and stone fruit tones that balance with both high and mid-range TDS. The PWN Golden Mandheling delivers heavy body and spice notes, ideal for testing lower TDS cups with 18–20% extraction. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.