Brew Strength Calculator
Turn a refractometer TDS reading into an extraction yield and see whether your coffee lands in the ideal range. Enter your dose, water, and measured strength. Calculates in your browser.
Extraction yield
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Show the math
Extraction yield is the share of the grounds that dissolved into the cup:
brewed coffee = water − (dose × 2)
extraction % = TDS% × brewed coffee ÷ dose
The SCA's sweet spot is roughly 18–22% extraction at 1.15–1.35% TDS. Under-extracted coffee tastes sour and thin; over-extracted tastes bitter. The grounds hold back about twice their weight in water, which is why the cup weighs less than the water in.
What this does
A brew strength calculator turns a refractometer TDS reading into an extraction yield and shows whether your coffee lands in the ideal range.
How to use it
- Enter your dose and water.
- Enter the measured TDS.
- Read the extraction yield.
- Compare it to the ideal range.
How it works
The SCA target is roughly 18–22% extraction at a balanced 1.15–1.35% TDS. Spent grounds hold back water, so the cup weighs less than the water poured.
extraction % = TDS% × brewed weight ÷ dose
Understanding your result
Extraction yield tells you how much of the grounds dissolved into the cup. The SCA sweet spot is roughly 18 to 22 percent: below it coffee tends to taste sour and underdeveloped, above it bitter and harsh. Adjust grind, time, or ratio to move the yield toward that band.
Example
1.3% TDS over a 36:1 brew lands near a 20% extraction.
Sources & methodology
Last updated .
Frequently asked questions
What is extraction yield?
It is the percentage of the ground coffee that dissolved into your cup, calculated as TDS% × brewed weight ÷ dose. The SCA target is roughly 18–22%.
What is TDS?
Total dissolved solids is the strength of the brewed coffee, measured as a percentage with a refractometer. A balanced cup sits around 1.15–1.35%.
Why is the cup lighter than the water I added?
The spent grounds hold back about twice their own weight in water, so the brewed coffee weighs less than the water you poured in.
Is my data stored?
No. Everything is calculated locally in your browser.
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