A coffee-to-water ratio expresses two weights in relation to each other. At 1:15, every gram of dry coffee is paired with fifteen grams of brewing water. Fifteen grams of coffee therefore calls for 225 grams of water. This arithmetic is the useful foundation of the source's ratio calculator: it lets a recipe be scaled without changing that relationship.
The meaning of the second number needs care. A filter-coffee recipe usually describes the water added to the brewer. Espresso commonly uses a dose-to-yield ratio instead, comparing dry coffee with the liquid collected in the cup. An 18-gram dose at 1:2 targets 36 grams of beverage; that is not an instruction to add only 36 grams of water to a machine reservoir. A cold-brew concentrate also needs its subsequent dilution recorded.
A ratio establishes a starting recipe, not a guaranteed extraction or flavour. Grind, water, temperature and the brewing process still influence the result. Record the ratio alongside those details, then make a deliberate adjustment based on the cup. This explanation preserves the source's practical calculation without suggesting that a calculator can select one universally correct recipe.
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