What is brew ratio and how to calculate it?
The brew ratio is the relationship between the mass of coffee and the mass of water used for a preparation, expressed in grams per litre (g/L) or as a fraction (1:15, 1:16, etc.). It is the most fundamental parameter of any coffee recipe: it determines the concentration and intensity of the final drink. The SCA's recommended range for filter coffee is 55 to 65 grams of coffee per litre of water.
The brew ratio is the quantitative expression of the coffee-to-water relationship — the most important parameter to master before tackling grind, temperature or time. Without a calibrated ratio, no other technique improvement will have a predictable effect on flavour.
The standard notation in specialty coffee: the ratio is expressed in two ways. Either in grams of coffee per litre of water (g/L) — for example, 60g/L means 60g of coffee for 1,000 ml of water. Or as a coffee:water fraction — 1:16 means 1 gram of coffee for 16 grams of water (water is generally weighed in grams too, as 1 ml of water = 1g at ambient temperature). These two notations are equivalent: 60g/L corresponds to a ratio of 1:16.7.
Standard ranges by method: the SCA recommends 55–65g/L for filter coffee, equivalent to a ratio of roughly 1:15 to 1:18. For espresso, the ratio is very different: approximately 1:2 to 1:3 (20g of coffee for 40–60g of liquid), which explains the concentration. For French press, 55–70g/L is common. For concentrated cold brew, up to 100–150g/L (1:7 to 1:10).
How to calculate: a simple proportion. Example: you have 20g of coffee and want a 1:15 ratio. Water needed = 20 × 15 = 300 ml. Or if you have a 500 ml brewer and want a 1:16 ratio: coffee = 500 / 16 = 31.25g (round to 31g). Always measure coffee with a precise scale to 0.1g and water in ml or grams. Spoons and volumetric measures for coffee introduce ±30% variability depending on bean density — an enormous error that makes any reproducibility impossible.
A surprising fact: the 'Golden Ratio' concept for filter coffee was formalised by the SCAA as early as the 1950s with a recommendation of 55g/L — a standard that has withstood 70 years of extraction research and remains the reference in global filter coffee competitions. This value is not arbitrary: it corresponds to a TDS (Total Dissolved Solids) range of 1.15–1.35% generally associated with maximum consumer satisfaction.
Reference brew ratios by method
| Method | Ratio (g/L) | Fraction ratio | Target TDS |
|---|---|---|---|
| Filter coffee (SCA standard) | 55-65 g/L | 1:15 to 1:18 | 1.15-1.35% |
| Espresso | ~100-125 g/L in basket | 1:2 to 1:3 in cup | 8-12% |
| Concentrated Aeropress | 80-100 g/L | 1:10 to 1:12 | 2-4% |
| Standard French press | 60-70 g/L | 1:14 to 1:17 | 1.2-1.5% |
| Concentrated cold brew | 100-150 g/L | 1:7 to 1:10 | 3-6% |
The Foundation Number of Every Coffee Recipe
Brew ratio is the single most important number in any coffee recipe because it determines the concentration and strength of the final cup before any other variable is considered. Expressed as the mass of coffee divided by the mass of water (e.g. 1:15 meaning 1g of coffee per 15g of water), the ratio is the recipe's anchor — changing it while holding all other variables constant will change the cup's strength and, indirectly, its perceived balance of flavour dimensions. A higher coffee-to-water ratio (more coffee per gram of water, like 1:12) produces a more concentrated, stronger cup; a lower ratio (less coffee per gram of water, like 1:18) produces a weaker, lighter cup. This sounds straightforward, but the relationship between ratio and cup quality is not linear in the way that adding more coffee simply makes the coffee better — there is an optimal concentration range for each brewing method and each coffee beyond which extraction balance deteriorates.
The interaction between ratio and extraction is the key complication. If you increase the dose (more coffee per gram of water) without adjusting grind size, the denser coffee bed will flow more slowly (in percolation methods) or reach extraction equilibrium more slowly (in immersion methods), both of which tend to increase extraction percentage relative to a lower dose at the same grind setting. Conversely, decreasing dose thins the bed, speeds flow, and may decrease extraction percentage. The practical implication is that ratio and grind size adjustments are not independent — changing one without considering the other can produce unexpected results. Experienced brewers often adjust ratio and grind together when moving between coffees, using the ratio to set target strength and the grind to set target extraction quality within that strength context.
Practical Recommendations
Establish your personal ratio baseline by brewing the same coffee at 1:14, 1:16, and 1:18 in your primary brewing method and tasting all three. The 1:14 will be noticeably stronger and may feel intense; the 1:18 will feel lighter and may emphasise acidity relative to sweetness. The ratio that produces the most pleasant balance for your taste is your personal baseline for that brewing method and coffee type. Record this alongside the coffee's origin and roast level — you will find that your preferred ratio shifts slightly between coffee types: body-forward Brazilians may be most satisfying at 1:14-1:15; bright Ethiopians may be most balanced at 1:16-1:17. This preference mapping, accumulated over several months of intentional tasting, is one of the most practically useful bits of self-knowledge a home coffee enthusiast can develop.