Coffee to Water Ratio by Brew Method (and Why It's by Weight)

Coffee ratio advice is full of round numbers with no source: “two tablespoons per six ounces,” “1:15 is the golden ratio,” “cold brew is 1:4.” Some of these are reasonable. Several are unit mix-ups. A brew ratio is just grams of water per gram of coffee, and it only means anything if both sides are weighed. The Specialty Coffee Association’s own number is 55 g of coffee per kilogram of water, which works out to about 1:18. Every other method, from French press to cold brew, starts from a stronger ratio for a specific reason. Below is what the SCA documents actually say, the ranges our coffee ratio calculator uses for each method, and worked numbers from the calculator’s own code.

What the SCA standard actually says

People often call it the “Golden Cup,” but the brewing numbers are spread across two different SCA documents, and they measure different things.

The SCA’s Coffee Standards (revised 2018), §5.1 “Golden Cup Standard,” doesn’t give a ratio at all. It defines the result:

Coffee shall exhibit a brew strength, measured in Total Dissolved Solids, of 11.5 to 13.5 grams per liter, corresponding to 1.15 to 1.35 “percent” on the SCA Brewing Control Chart, resulting from a solubles extraction yield of 18 to 22 percent.

The ratio comes from the SCA’s equipment standard. SCA Standard 310-2021 for home coffee brewers defines the “standard brew ratio” as “55 g of coffee per 1.000 kg of water.” It requires certified brewers’ instructions to recommend “a coffee/water ratio of 55 g/kg (or its equivalent in other units),” and it accepts a brew strength of 1.15–1.55% at that ratio. That strength ceiling is wider than the Golden Cup’s 1.35%. The same Coffee Standards document uses the identical proportion for cupping: 0.055 g of coffee per ml of water.

Converting 55 g/kg to the “1:R” form everyone uses:

1000 g water ÷ 55 g coffee = 18.18  →  1:18.2

So the SCA’s reference point sits at the mild end of the 1:15–1:18 range you’ll see in most brewing guides. A lot of blogs attach a “±10%” tolerance to the 55 g figure. Neither SCA document we read includes that tolerance, so we’ve left it out.

Why the ratio is by weight, not scoops

Coffee beans vary in density with roast and grind, so a spoon holds a different mass depending on the coffee. Our calculator converts grams to tablespoons at 5.5 g per level tablespoon (GRAMS_PER_TBSP in the source) and labels the result approximate. Stumptown’s V60 brew guide calls for “21g (3 Tablespoons) of ground coffee,” which is 7 g per tablespoon. That’s 27% more coffee per spoon than our conversion assumes.

Here’s why that matters. Take 500 g of water at 1:16:

Measured by	Coffee	Actual ratio
Scale	31.25 g	1:16
5.7 level tbsp, if your tbsp is 5.5 g	31.25 g	1:16
5.7 level tbsp, if your tbsp is 7 g	39.8 g	1:12.6

Same recipe, same spoon count, and the second cup lands in French-press strength without you changing anything. Water is the easy side: 1 ml weighs about 1 g, so a gram scale measures both, and our calculator treats ml and g of water as the same thing.

Ratio ranges by method

This is the method table from our calculator’s source (METHODS in src/lib/everyday/coffee-ratio-calculator.ts), reproduced exactly. The strength slider moves across each range, and its midpoint is the default.

Method	Range	Slider midpoint	Our note
Pour-over (V60, Kalita, Chemex)	1:15 – 1:17	1:16	1:16 is a common starting point. Medium-fine grind; 3–4 minute total brew.
French press	1:12 – 1:15	1:13.5	Coarse grind, 4 minute steep, then press gently.
AeroPress	1:6 – 1:12	1:9	Low ratios make a concentrate you can top up with hot water.
Drip coffee maker	1:15 – 1:18	1:16.5	Medium grind. Coffee-maker “cups” are usually 5–6 fl oz, not 8.
Cold brew concentrate	1:4 – 1:8	1:6	Coarse grind, steep 12–24 h in the fridge, then dilute about 1:1 with water or milk.
Espresso (by yield)	1:1.5 – 1:2.5	1:2	1:2 is the modern standard (18 g in → 36 g out). 1:1–1:1.5 is ristretto; 1:3 is lungo.
Moka pot	1:7 – 1:10	1:8.5	Fill the basket level without tamping; water to just below the valve.

These are starting points, not standards. None of the ranges quite reaches the SCA’s 1:18.2: drip gets closest at 1:18, so type 18.2 into the custom field if you want the SCA figure exactly. The immersion and concentrate methods are stronger on purpose.

For a real-world check, Stumptown’s V60 recipe is 21 g of coffee to 360 g of water, or 1:17.1. That falls inside our pour-over range, near the mild end.

Espresso is measured by what comes out

Every other ratio in the table is coffee to water in. Espresso is coffee to beverage out. The machine keeps pushing water through the puck until you stop the shot, so the water going in isn’t a useful number. Baristas weigh the dry dose and the liquid espresso in the cup.

Our calculator marks espresso with a byYield flag and handles it differently:

18 g dose at 1:2  →  36 g espresso in the cup

For espresso, the “water” field means yield, the in-cup amount equals the yield, and the calculator doesn’t subtract any water for the grounds. Weigh the shot on a scale under the cup instead of reading the lines on a shot glass. As our calculator’s FAQ puts it, the yield “includes dissolved coffee and crema,” so volume markings aren’t a reliable measure.

Concentrates: cold brew and AeroPress

Cold brew’s 1:4–1:8 range looks very strong because it isn’t the drink yet. You’re making a concentrate to dilute later. Counter Culture’s cold brew guide is a good published example: a “1:8 ratio—1 gram of coffee for every 8 grams of water,” about 125 g of coffee per liter, “14 hours is a good place to start” in the fridge, then a “concentrate-to-water ratio between 2:1 and 1:1” to serve. Its 1:8 is the mildest end of our cold-brew range.

Running that recipe through our calculator:

125 g coffee × 8 = 1,000 g water
concentrate ≈ 1,000 − 2 × 125 = 750 g   (grounds keep ~2 g water per g)
diluted 1:1  → about 1,500 g to drink

Our calculator gives you the concentrate numbers and a reminder to dilute about 1:1. It doesn’t work out the final diluted drink, so do that last step yourself. If the ratio is so strong that you can’t solve it by number of cups, the calculator will say so, for example a 1:2 AeroPress: “Ratio is too strong to solve by servings — solve from water instead.”

AeroPress is a bit different. The official AeroPress instructions measure coffee in grams (“1 heaping Scoop or 16-18 grams”) but measure water by the numbered marks on the chamber (“up to the 4”), with no ml figure for those marks. That means you can’t get a gram ratio from the official recipe without weighing the water yourself. Our 1:6–1:12 range covers both the concentrate style (1:6 from 17 g of coffee is 102 g of water) and a direct, drink-as-is cup.

Strength is not extraction

Ratio sets strength, meaning how concentrated the cup is (TDS). Grind, time and temperature set extraction, meaning what fraction of the coffee dissolved. The Golden Cup range covers both, and they’re linked by one equation:

TDS % ≈ extraction % × coffee ÷ beverage
beverage ≈ water − 2 × coffee        (our calculator's retention assumption)

Plugging in the ratios, per gram of coffee:

Ratio	TDS at 18% extraction	at 20%	at 22%
1:15	1.38%	1.54%	1.69%
1:16	1.29%	1.43%	1.57%
1:17	1.20%	1.33%	1.47%
1:18.2 (SCA)	1.11%	1.24%	1.36%

These are our own calculations, and the 2 g/g retention is an approximation, so treat the second decimal loosely. The pattern still matters. At the SCA’s 1:18.2, an 18–22% extraction lands at 1.11–1.36% TDS, which matches the Golden Cup’s 1.15–1.35% almost exactly. At 1:15, even a perfect 20% extraction gives 1.54%, stronger than the Golden Cup allows. Neither brew is wrong. They’re just different strengths.

This is also why “my coffee tastes weak, so I’ll add more coffee” is sometimes the wrong fix. A thin, sour cup at 1:16 can be under-extracted (grind too coarse, brew too short) rather than under-dosed. Adding coffee raises strength but doesn’t fix the sourness. The FAQ on our calculator page makes the same point: “Ratio controls strength, while grind and time control extraction, so change one variable at a time.” Our calculator only handles the ratio. It doesn’t measure or estimate TDS or extraction, since that needs a refractometer.

Scaling for N cups: the grounds keep some water

“Four 8 oz cups at 1:16” looks like simple multiplication, but it comes up short:

naive:   4 × 237 ml ÷ 16 = 59.3 g coffee   (brews ~948 ml of water, but you pour out less)

Wet grounds hold on to water. Our calculator assumes about 2 g of water per gram of coffee (ABSORPTION = 2) and solves for what ends up in the cups:

coffee = beverage ÷ (ratio − 2) = 948 ÷ 14 = 67.7 g
water  = 67.7 × 16            = 1,083 g
in the cups ≈ 1,083 − 2 × 67.7 = 948 ml  ✓

That’s about 8.5 g more coffee than the naive version, and 135 g more water. The retention figure lines up with published recipes. Stumptown’s 21 g / 360 g V60 says it yields “about 10 oz,” and our model gives 360 − 42 = 318 g, or 10.75 fl oz.

Cup size makes an even bigger difference. Our cup presets start at a 6 oz “coffee-maker cup” (177 ml) because carafe markings often use cups smaller than a mug. Check the lines on your own carafe. Ten cups at the drip midpoint of 1:16.5:

“Cup”	Coffee	Water	In the carafe
6 oz (177 ml)	122.1 g	2,014 g	≈ 1,770 ml
8 oz (237 ml)	163.4 g	2,697 g	≈ 2,370 ml

If you follow an 8 oz recipe in a machine marked in 6 oz cups, or the other way around, you’ll be off by about a third.

Using the calculator

Open the coffee ratio calculator and pick a method. Then choose what you already know: the water in your kettle, the coffee you have left, or how many cups you want. It gives grams of coffee and water, approximate tablespoons, and approximately how much ends up in the cup. Everything runs in your browser. For steep times, the countdown timer works well for a 4-minute French press or a 14-hour cold brew. For a recipe in ounces, the unit converter handles it.

Other kitchen and table math

Rice is the opposite case: it’s measured by volume, and the ratio depends on the pot. The rice to water ratio calculator uses the USA Rice Federation’s 2:1 for long-grain white rice on the stovetop but 1:1 in an Instant Pot, because a sealed pot loses almost no water to steam. For drinks, the cocktail dilution calculator counts melted ice as an ingredient. Its presets use common bar rules of thumb, 20–25% added water for stirred drinks (default 22.5%) and 25–40% for shaken (default 30%). Its own notes point out that Dave Arnold’s measurements run higher. On Cooking Issues he measured a stirred Manhattan at 50% dilution and a shaken whiskey sour at 63%, and wrote that the popular 25% figure is “Not true.” Weigh a drink before and after mixing once, then type your own number into the custom field. If “percent of the undiluted volume” sounds slippery, percentage points vs percent change covers the general trap. And when the bill comes, the tip calculator splits it to the cent and can tip on the pre-tax amount.