Understanding Extraction — The Key to Great Coffee
Every coffee bean is roughly 30% soluble — the rest is woody plant material that stays in the grounds. Extraction yield (EY%) is the percentage of those solubles you actually pull into your cup, and it's the single most important number in brewing. This coffee extraction calculator works it out for you from your dose, yield, and TDS.
Decades of Specialty Coffee Association research point to a sweet spot of 18–22% extraction. Below 18% you pull acids and salts but miss the sugars, so the cup tastes sour and sharp. Above 22% you start dissolving bitter, astringent compounds, so the cup turns dry and harsh. The goal of dialing in is simply to land inside that window.
EY% vs. TDS — what's the difference?
TDS (Total Dissolved Solids) is how strong the cup is — how concentrated the brew tastes. Extraction yield is how much flavor you pulled from the grounds. You can have a strong but under-extracted cup, or a weak but perfectly extracted one. That's why a coffee TDS calculator on its own isn't enough — you need both axes, which is exactly what the Brewing Control Chart plots.
The taste cheat sheet
- Tastes sour? Under-extracted — to fix under-extracted coffee, grind finer or brew longer.
- Tastes bitter? Over-extracted — to fix over-extracted coffee, grind coarser or brew shorter.
- Tastes weak? Too little coffee — add 1–2g of dose.
- Tastes heavy? Too much coffee — use 1–2g less, or add water.
How to Use a Refractometer
For those who want to go deeper, a refractometer turns guesswork into precise measurement. It's optional — tasting works for 99% of home brewers — but it's the fastest way to nail repeatable results.
- Brew as normal, then draw a small sample and let it cool to room temperature (hot samples read inaccurately).
- Filter the sample through a syringe filter if your method leaves fines (French press, espresso).
- Place 2–3 drops on the sensor, close the lid, and read the TDS percentage.
- Enter that TDS above along with your dose and yield — the calculator returns your exact extraction yield and plots it on the chart.
Dialing in espresso specifically? Pair this with our Espresso Recipe Builder, or perfect your brewing water first with the Water Chemistry Advisor.