Tasting
Measuring extraction yield
The measurement that separates strength from extraction — two things taste alone conflates, and which need opposite fixes.
- Skill level
- Advanced
- How long it takes
- A few minutes per measurement
- Equipment needed
- Coffee refractometer, Digital scale
- Steps
- 6
Why it works this way
A refractometer measures how much dissolved material a brew contains, expressed as total dissolved solids. On its own that is strength: how concentrated the drink is. Combined with the dose and the beverage weight it gives extraction yield — what proportion of the ground coffee actually dissolved — and that is a different property entirely. A weak-tasting brew might be under-extracted, needing a finer grind, or perfectly extracted and simply dilute, needing more coffee. The two fixes are opposite and taste alone frequently cannot tell them apart. What the number cannot do is tell you whether the coffee is good. A brew inside any published target range can taste unpleasant, and plenty of excellent coffee sits outside one. Extraction yield explains what you tasted; it does not replace tasting.
What you need
Helpful, not essential
How to do it
Weigh the dry dose and the finished beverage.
Beverage weight, not brew water. The grounds retain a substantial amount, and using brew water instead inflates the result badly.
Calibrate the refractometer with distilled water at the start of the session.
An uncalibrated instrument produces precise readings of the wrong thing.
Take a sample and cool it to the instrument's stated temperature range.
Readings drift with temperature. A hot sample is the single most common source of inconsistent numbers.
For espresso, cool and stir the sample thoroughly, and filter it if your instrument's instructions call for it.
Espresso carries suspended solids and undissolved material that scatter light. This is why espresso readings are less reliable than filter ones.
Read the TDS percentage, then calculate: yield = beverage weight × TDS ÷ dose.
The result is the percentage of the dry coffee that ended up dissolved in the cup.
Write the number beside your tasting note, not instead of it.
The number's value is that it explains a difference between two brews you tasted. On its own it explains nothing.
How to tell it worked
Not a sensory result. What it gives you is the ability to say whether a thin cup was under-extracted or merely dilute, which taste alone often cannot.
If it did not work
What you saw, what to change, and why the change works.
Low yield and a sour, thin cup
Change: Grind finer, or extend the contact time.
Under-extraction: not enough of the coffee dissolved, and the compounds that arrive first are the sharp ones.
Normal yield but a weak-tasting cup
Change: Use more coffee for the same water.
This is a concentration problem, not an extraction one. Grinding finer would over-extract a brew that was already fine.
High yield and a drying, bitter cup
Change: Grind coarser or shorten the brew.
Over-extraction pulls out the compounds that arrive late.
Readings vary widely between samples of the same brew
Change: Cool and stir more thoroughly, and check the calibration.
Temperature and undissolved material are the two usual causes, and both are procedural rather than about the coffee.
Common mistakes
Using brew water instead of beverage weight
The yield comes out substantially too low, because a large part of the water never reached the cup.
Instead: Weigh what is in the cup.
Chasing a target percentage
Brews that measure well and taste worse than the ones being abandoned.
Instead: Use the number to explain what you tasted, never to overrule it.
Treating espresso readings as equal to filter readings
Confident conclusions from the least reliable measurement the instrument makes.
Instead: Treat espresso numbers as indicative, and compare them only against your own other espresso numbers.
Diagnose a specific problem
The science behind it
- Total dissolved solids (TDS)
A measurement of how concentrated your brewed coffee is.
- Extraction yield
The percentage of the original ground coffee's dry weight that ended up dissolved in your cup.
- Extraction
How much of the coffee's flavour has actually dissolved into the water — too little tastes sour or thin, too much tastes bitter or harsh.
- Strength (intensity)
How concentrated a brew tastes — separate from how it was extracted.