Brew Ratios

Why 1:16 became the filter default, what changes as you move away from it, and why espresso and cold brew use completely different numbers.

A brew ratio is water mass divided by coffee mass. "1:16" means 16 g of water for every 1 g of coffee — 25 g of coffee to 400 g of water.

Always work in grams. Scoops and millilitres of grounds vary wildly with roast level and grind, because roasting changes bean density by a third or more¹; a scale that reads to 0.1 g is the single highest-value piece of gear you can buy.

Filter coffee: 1:15 to 1:18

The SCA "Golden Cup" standard is 55 g of coffee per litre of water, or about 1:18². Most specialty cafés brew a touch tighter, 1:15 to 1:17, and almost every popular pour over recipe lands in that band; this is practice, documented by practitioners rather than by a standard³¹.

Move the ratio and strength moves with it:

Tighter (1:14, 1:15) — more body, more intensity, slightly lower extraction because each gram of coffee sees less fresh water.
Wider (1:17, 1:18) — lighter, more transparent cup, slightly higher extraction because there is more solvent per gram.

The extraction shift is small; the strength shift is large. Extraction is driven by the concentration gradient between the inside of the particle and the water around it, so more water per gram keeps that gradient steeper for longer⁴; strength is simply dissolved coffee divided by beverage, so it moves in direct proportion to the water you add. That is the main reason to think of ratio as your strength knob and grind as your extraction knob⁵.

InteractiveRatio and strength

Ratio sets strength; extraction sets flavour balance. Hold extraction still and slide the ratio to see strength move — then change extraction and see how little the ratio matters to it.

Dose20 g

Ratio1:16.7

Extraction yield20 %

Water to pour

334 g

Beverage

292 g

42 g stays in the grounds

Dissolved coffee

4.00 g

Strength (TDS)

1.37 %

In the window. Strength is right; now let flavour decide whether extraction should move.

How this is computed: water = dose × ratio; beverage = water − dose × 2.1 g/g retained in the spent grounds (typical for paper-filter brews; immersion retains more, espresso less); dissolved = EY × dose; TDS = dissolved ÷ beverage. The 1.15–1.45 % strength window is the SCA filter standard (its 2020s revision widens the acceptable range); 1:15–1:17 is where that window and 18–22 % EY overlap. Sources: [2] [5] [1]

Espresso: 1:1.5 to 1:3

Espresso ratios describe beverage out : dry coffee in, not water in. A "1:2" shot is 18 g in, 36 g out.

Style	Ratio	Character
Ristretto	1:1 – 1:1.5	syrupy, intense, lower extraction
Normale	1:2 – 1:2.5	the modern default; ~9 % TDS
Lungo	1:3 – 1:4	lighter body, higher extraction, less bitterness
Turbo / allongé	1:3+ in ~15 s	coarse grind, low pressure, very clean

The style names and TDS figures are practitioner conventions³. The extraction trend is measured: a 2020 modelling-and-experiment study of espresso found extraction yield rising as more water passed through the puck at a given dose, and that high-yield, reproducible shots came from coarser grinds, lower doses and longer ratios rather than from the traditional fine-and-tight recipe⁶. Espresso can hit 18–22 % extraction at 1:2 only because pressure, fine grind and high temperature drive extraction fast. Push the ratio longer and you can pull 23–25 % from a light roast without harshness — the extra water dilutes the bitter compounds even as it extracts them. That last observation is practitioner experience³, consistent with the 2020 study but not itself measured there.

Immersion: 1:12 to 1:17

French press and AeroPress grounds stay in contact with all the water for the whole brew, so the extraction is more even but the concentration gradient falls as the brew proceeds⁴. Immersion brews usually taste best a touch tighter (1:13–1:15) than the same coffee as a pour over, and AeroPress users often brew a concentrate at 1:6 and dilute afterwards — called bypass brewing. Both are Cup Engineering practice notes, consistent with practitioner guidance³.

Cold brew: 1:4 to 1:8 concentrate

Cold water extracts slowly. Brewing 12–24 hours at 1:8 produces a concentrate that is diluted 1:1 before serving; Cup Engineering's model assumes about 18 % extraction under those conditions, which puts the concentrate around 2–3 % TDS. Those figures are working assumptions from our model, not measurements. Brewed "ready to drink" at 1:15 the cup is often thin and under-extracted; the concentrate-and-dilute approach gets more out of the coffee.

A quick reference

Method	Typical ratio	Water for 20 g coffee
Pour over	1:16 – 1:17	320–340 g
French press	1:15	300 g
AeroPress	1:12 – 1:14	240–280 g
Moka pot	1:7 – 1:10	140–200 g
Espresso (out:in)	1:2	40 g beverage
Cold brew concentrate	1:8	160 g

These are the defaults Cup Engineering's calculator starts from (lib/coffee.ts); they summarise common practice³¹ and are not standards.

How the numbers are computed

water     = dose × ratio                       g
beverage  = water − dose × retention           g     retention: g water held per g coffee
dissolved = EY / 100 × dose                    g
TDS       = dissolved / beverage × 100         %

Worked example at fixed extraction: 20 g of coffee at 20 % EY dissolves 4.0 g whatever the ratio. At 1:15 (300 g water, 258 g beverage after 2.1 g/g retention) that is 1.55 % TDS; at 1:17 (340 g water, 298 g beverage) it is 1.34 %. The ratio moved strength by 15 % while extraction, by construction, did not move at all. In practice extraction drifts up slightly with a wider ratio; the calculator models that as 0.8 % EY per doubling of the ratio, a Cup Engineering working assumption that captures the direction of the gradient effect⁴ rather than a measured coefficient. Retention values per method are also Cup Engineering parameters, chosen from typical practitioner measurements of about 2 g/g for filter brews¹.

Use the calculator to see how ratio interacts with grind, temperature and time for any of these methods.