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Coffee Extraction Calculator

Find your extraction yield and strength for a dialed-in brew.

Result

21.00%
1.40%

How it is calculated

The tool works out how much of the dry coffee ended up in the cup: extraction % = (TDS ÷ 100 × beverage mass) ÷ dose × 100. TDS is the strength read from a refractometer, as a percentage of the liquid; beverage mass is the weight of the finished drink in grams; dose is the dry ground coffee in grams. The numerator is the grams of dissolved solids in the cup. Strength is your TDS shown back as a percentage. Both are given with two decimals. Impossible inputs show no result: a dose of zero or less, a negative TDS or mass, a TDS above 100, or an extraction that would come out above 100 % (more solids than the dose itself). The tool does not judge the figure; the filter-coffee target of about 18 to 22 % is your own reference.

Worked example

A filter brew uses a 20 g dose and yields 300 g of coffee in the cup; the refractometer reads a TDS of 1.40. Dissolved solids in the cup: 1.40 ÷ 100 × 300 = 4.2 g. Divide by the dose: 4.2 ÷ 20 = 0.21, which as a percentage is 21.00% extraction. Strength is shown as 1.40%. A result of 21 % sits inside the commonly quoted 18 to 22 % window, so grind and time would be left alone.

Try this example →

Common mistakes

  • Entering the weight of the water poured instead of the beverage mass. The grounds hold back water, so the cup weighs less than the water that went in, and extraction comes out overstated.
  • Typing TDS as a fraction, such as 0.014. The field is in percent, so 1.4 percent is typed as 1.4; 0.014 would give an extraction of just 0.21%.
  • Reading a hot sample without letting it cool, which gives a falsely high TDS.
  • Entering the wrong weights for espresso. Use the weight of the espresso in the cup and the dry dose, not the water the machine used.
  • Reading the result as a verdict on taste. The tool gives a number, and a cup inside 18 to 22 % can still taste unbalanced.

About this calculator

Coffee extraction yield measures what percentage of the ground coffee's mass actually dissolved into your cup, calculated from Total Dissolved Solids (TDS, measured with a refractometer): Extraction % = (TDS × brewed weight) / dose weight. The widely used “Coffee Brewing Control Chart” from the SCA (Specialty Coffee Association) puts the ideal extraction window at roughly 18-22%, with strength (TDS) typically targeted around 1.15-1.35% for filter coffee.

Under-extraction (below 18%) tastes sour and underdeveloped because desirable acids and sugars haven't fully dissolved yet, while over-extraction (above 22%) pulls out bitter, astringent compounds from the coffee grounds — baristas and home brewers adjust grind size, brew time, water temperature and dose-to-water ratio to steer both numbers into the target range.

Pair your refractometer's TDS reading with the dose and the brewed weight to see extraction yield and brew strength, the two numbers that let you repeat a cup you liked.

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