Coffee to Water Ratio Calculator

How the Coffee Ratio works

Coffee to water ratio: the one number that fixes most bad cups

Bitter, thin, sour, muddy: most complaints about home coffee trace back to the dose, not the beans. Scoops vary by 30% depending on roast and grind, because dark beans are lighter and puffier than light ones, so a "two scoops per mug" habit drifts every time you change bags. Weighing coffee and water, and holding them at a fixed ratio, removes that variable. Once the ratio is stable you can change one thing at a time, grind, temperature or time, and actually taste the difference.

The formula

The ratio is written 1:R, meaning R grams of water for every gram of coffee.

• Coffee (g) = water (g) ÷ R
• Water (g) = coffee (g) × R
• Strength in g per litre = 1000 ÷ R

Water weighs 1 g per mL at brewing temperatures to within about 4%, so millilitres and grams are interchangeable on a kitchen scale. The page also estimates the brewed yield as water minus twice the coffee weight, because spent grounds hold roughly double their weight in liquid.

Worked examples

Example 1: a 500 mL pour-over at 1:16. 500 ÷ 16 = 31.3 g of coffee, about 5.2 level tablespoons, at 63 g per litre. The grounds keep around 62 mL, so about 438 mL reaches the cup.

Example 2: an AeroPress with 18 g of coffee. 18 × 14 = 252 mL of water, 71 g per litre, and roughly 216 mL of coffee to drink.

How many grams of coffee per cup? It depends on the cup. A 250 mL mug at 1:16 needs 15.6 g, which is close to the "two tablespoons per six ounces" rule printed on many American bags. A 150 mL European cup needs about 9.4 g. Grams of coffee for common amounts of water at five brew ratios

Read across a row to see how much a change of method moves the dose: 500 mL is 50 g in a moka pot but under 30 g at 1:17.

How to read the result

• Coffee is the dose to one decimal place, with a level tablespoon taken as 6 g. Treat the tablespoon figure as a fallback; ground coffee varies from about 5 to 7 g per spoon.
• Water is the brewing water in grams and millilitres.
• Ratio repeats the ratio and gives it as grams per litre, the unit brewing standards use.
• Brewed yield is what you will actually pour. For espresso this line changes: the ratio is measured on the liquid in the cup, not water going in, so the Water line becomes "Espresso in the cup". An 18 g dose at 1:2 gives 36 g of espresso.

Where the standard ratios come from

The Specialty Coffee Association's Golden Cup standard targets about 55 g of coffee per litre, close to 1:18, with 18 to 22% of the coffee's mass extracted and a strength of 1.15 to 1.35% dissolved solids. Most cafés brew a little stronger, which is why 1:15 to 1:17 are the common defaults. French press sits slightly stronger because immersion extracts less evenly. Moka pots run near 1:10 because their small basket is filled to the brim. Cold brew is usually made as a 1:5 concentrate over 12 to 24 hours and diluted 1:1 with water or milk before drinking.

Tips and pitfalls

• Fix the ratio, then adjust grind. If a cup at 1:16 tastes sour or thin, grind finer; if it is bitter or dry, grind coarser. Changing the dose at the same time makes it impossible to tell which change helped.
• Weigh the water too. A kettle's markings can be out by 50 mL, which at 1:16 is three grams of coffee.
• Don't dilute to fix strength. If you want weaker coffee, brew at 1:17 or 1:18 rather than topping up a strong cup; over-extracted flavours stay bitter however much water you add.
• Scale cold brew by the concentrate. One litre of 1:5 concentrate uses 200 g of coffee and makes about two litres to drink once diluted.

The tablespoons to grams and cups to grams converters handle other ingredients by volume, and the recipe scaler resizes a whole recipe at once.

Sources: Specialty Coffee Association brewing protocols.

Checked against: SCA golden cup: 55 g coffee per litre of water

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