Coffee dose for a target water amount and brew strength.
Standard SCA brewing ratios fall between 1:14 (strong) and 1:18 (mild). Adjust to taste.
The single biggest variable in a great cup of coffee, after the freshness of the beans, is the ratio of water to ground coffee. Get it wrong by even a few grams and a brew that should taste balanced becomes either harsh and overly bitter or weak and watery. Professional baristas, third-wave coffee shops, and the home enthusiasts who follow them have settled on a narrow window of brewing ratios that consistently extract the desirable compounds (sweetness, acidity, body) while leaving behind the harsh ones (over-extracted bitterness, papery dryness, sour underdevelopment). This calculator turns that window into hard numbers: tell it how much water you plan to brew with, pick a strength on the slider, and read off the exact mass of ground coffee to weigh out. Once you start measuring instead of guessing, the variability drops out of your morning cup, and any debugging — too sour? too bitter? — becomes a question of grind size and water temperature rather than dose.
A coffee ratio is simply mass of water divided by mass of coffee:
coffee mass = water mass / ratio
If your scale uses millilitres for water and grams for coffee, the conversion is one-to-one because 1 ml of water at room temperature weighs essentially 1 g (the actual density of water at 20 °C is 0.998 g/ml — close enough for kitchen scales). So a 16:1 ratio with 480 ml of water gives 480 / 16 = 30 g of coffee. The Specialty Coffee Association's published "golden cup" range corresponds to a ratio between roughly 14:1 and 18:1, with 16:1 considered the canonical neutral starting point. Below 14:1 the coffee is "stronger" but typically over-concentrated; above 18:1 it tends to taste under-developed and thin.
The panel takes three inputs: the water amount (with a metric/imperial unit toggle for ml or fl oz), the brew strength ratio between 12:1 (very strong) and 20:1 (very mild) on a slider, and the output unit (grams or ounces) for the resulting coffee dose. The result panel shows the exact ground-coffee mass to weigh, the original water amount restated for confirmation, the ratio you selected as a colon-separated pair, and a strength label (Strong / Standard / Mild / Weak). Default values are 500 ml of water at a 1:16 ratio, which yields 31.25 g of coffee — a typical V60 dose for two cups.
You want to brew a single 12-oz pour-over (about 355 ml of water). Switch the unit to fl oz, set water to 12, leave the ratio at 16. The calculator converts 12 fl oz to 354.9 ml internally, then divides by 16 to give a coffee dose of 22.2 g. Compare to a French press for two people: enter 800 ml at a 15:1 ratio (the slightly stronger end suits immersion brewing) and you get 53.3 g of coffee — about three rounded tablespoons. For a Chemex three-cup, 600 ml at 17:1 gives 35.3 g, slightly milder to compensate for the higher temperature throughout the long bloom. As you slide the ratio from 14 to 18 with the water held constant, watch the dose drop linearly — a 25 % change in ratio is a 25 % change in coffee mass.
First, weighing water by volume but coffee by tablespoon is the most common mistake. Tablespoons of ground coffee vary by 50 % or more depending on grind size; only a digital scale (in grams) eliminates this drift. Second, ignoring water absorption: the spent grounds retain about 2 ml of water per gram of coffee, which means your final beverage is smaller than the input water. For a single cup at 16:1 with 250 ml of water, expect ~220 ml in the cup. Third, treating the ratio as a substitute for grind size. A 16:1 ratio is correct in mass but the coffee will still taste bitter if the grind is too fine, or sour if too coarse — strength is one knob, extraction is another. Fourth, applying a pour-over ratio to espresso. Espresso runs at far stronger ratios (1:2 to 1:3 yield) by design and is computed differently. Fifth, forgetting that immersion methods (French press, AeroPress) tolerate slightly stronger ratios than percolation methods (V60, Chemex), because they leave more dissolved solids in the cup.
The 1:16 ratio comes from the SCA "Golden Cup" standard: 1.15 g/L to 1.35 g/L of total dissolved solids in the cup, achieved at extraction yields between 18 % and 22 %. Different methods land in slightly different parts of this window. The aeropress recipe community commonly uses 1:14 to 1:16 for an inverted brew, and 1:12 for the famous "Tim Wendelboe" recipe. Cold brew runs at much higher concentration (1:4 to 1:8) because it is intended to be diluted before drinking. Espresso is traditionally specified by yield ratio: 1:2 means 18 g of coffee yields 36 g of beverage, generally pulled in 25 to 30 seconds. Turkish coffee is closer to 1:7 because it is consumed unfiltered with the grounds in suspension. Across all of these, the underlying physics is the same: extraction is a function of contact time, temperature, surface area (grind), and ratio. Holding three of those constant lets you tune the fourth deliberately.