Extraction in one paragraph
Water dissolves compounds out of coffee grounds. Early in the process it pulls acids and bright fruity notes. Later it draws out sugars and caramelised sweetness. Push further and it starts extracting harsh, bitter, astringent compounds.
Under-extracted coffee tastes sour, sharp and thin. Over-extracted coffee tastes bitter, dry and hollow. The target is the middle, where sweetness balances acidity and the finish is clean.
Grind size controls how fast this happens. Finer grinds expose more surface area and extract faster; coarser grinds slow everything down.
Weigh everything. Volume scoops vary by thirty percent or more depending on grind and settling, which makes them useless for repeatability.
Ratio and what it changes
Ratio is the weight of coffee to the weight of water. A common starting point for filter coffee is one to sixteen - sixteen grams of water for every gram of coffee.
Filter brewing generally sits between one to fifteen and one to eighteen. Espresso runs from one to one point five to one to two point five, dramatically stronger because of the pressure involved.
Changing ratio changes strength and extraction at the same time. A stronger ratio with the same grind will extract less proportionally but taste more concentrated. Adjust one variable, taste, then adjust the other.
Freshly roasted coffee degasses for several days. Brew it too soon and the escaping carbon dioxide disrupts extraction, which is why a short rest makes a noticeable difference.
Starting points by method
Pour over, such as a V60: medium-fine grind, ratio around one to sixteen, water around 93 degrees, total brew time between two and a half and three and a half minutes.
Espresso: fine grind, ratio between one to one point five and one to two point five, water around 93 degrees, extraction between twenty-five and thirty-two seconds.
French press: coarse grind, ratio around one to fifteen, water just off the boil, four to five minutes of contact time before pressing.
AeroPress: medium-fine grind, ratio one to fifteen, water around 85 degrees, one and a half to two and a half minutes.
How to adjust
If the coffee tastes sour or thin, extract more: grind finer, increase temperature slightly, or extend contact time. Change one thing at a time.
If it tastes bitter or dry, extract less: grind coarser or shorten the contact time. Bitterness that appears at the very end of the cup is usually over-extraction from the last part of the brew.
Use our extraction and ratio calculator to work out water volumes for a given dose and ratio, then fine-tune by taste from there.
Educational content. Roast Lab publishes reference material only. We do not sell coffee, equipment or accessories, and we do not guarantee any specific roasting result. Coffee roasting involves high temperatures, hot surfaces and combustible chaff - always follow your equipment manufacturer instructions, ensure adequate ventilation, never roast unattended, and keep a suitable fire extinguisher within reach. Caffeine-sensitive individuals should consult a healthcare professional about intake.