Brew Ratio Calculator

The ratio calculator answers one question three different ways: given a coffee dose, how much water do you need; given a water amount, how much coffee; or given a number of cups, both figures at once. Every one of the 18 methods on this site has its own ratio built in, because a French press and an AeroPress don't share a "correct" ratio even though both are simple immersion brewers — the worked example on this page shows a pour-over at balanced strength as a concrete illustration of the arithmetic before you plug in your own numbers.

Why direction matters

Most people start from whichever number they already know. If you've measured a dose of beans on a scale, you want water calculated from coffee. If you're filling a specific carafe or kettle to a marked line, you want coffee calculated from water. If you're just making "two cups," you want both figures worked out from a cup count, using either the method's typical serving size or a custom one — genuinely useful since a "cup" varies by method: a full 240ml mug for drip coffee, a 30ml shot glass for espresso.

The math behind it

Every method's ratio is expressed as 1 part coffee to N parts water by weight, where 1 gram of water is treated as 1 millilitre — the standard brewing assumption, accurate enough that no home scale can tell the difference. Divide water by N to get coffee; multiply coffee by N to get water. Espresso is the one exception worth knowing about: its ratio describes the liquid that comes out of the puck (the yield), not the water poured in, because some water stays behind in the spent grounds. The calculator handles that distinction automatically based on which method you pick.

Three strengths, not one number

Light, balanced and strong aren't quality judgments — they're starting points for different roasts, different taste preferences, and different reasons for brewing (a shot pulled to add to milk usually wants more concentration than one drunk on its own). If a ratio in any preset tastes wrong, the method guide and fix pages for what's actually off are the next step, not just nudging the ratio further in the same direction.

Cup size is genuinely inconsistent

A "cup" of coffee is a surprisingly slippery unit. A US legal cup is 240ml, but the markings on most drip machine carafes actually correspond to roughly 150ml (5oz) per "cup" — which is a common source of a stronger or weaker pot than intended when someone measures coffee for the number of markings rather than the actual volume of water in the reservoir. The calculator lets you set an exact cup size in millilitres so this ambiguity doesn't quietly wreck your ratio.