How the coffee-to-water ratio calculator works
Coffee brew ratio is a simple weight relationship: for every 1 part (gram) of ground coffee, you use N parts (grams) of water. The calculator's formula is water (g) = coffee dose (g) × N, where N is the ratio number you choose or select from a preset. Because water at brewing temperature has a density very close to 1 g/ml, grams of water and milliliters of water are effectively interchangeable for this purpose — 236 g of water is about 236 ml.
Why weight, not volume
Ground coffee's volume varies with grind size, roast, and bean density, so a "tablespoon of coffee" is not a reliable unit — the same tablespoon can hold anywhere from about 5 g to 7 g of grounds depending on grind and roast. Weighing both coffee and water on a kitchen scale removes that variability and is the method recommended by the Specialty Coffee Association (SCA) and virtually every professional barista training program.
Common brew ratios
- Espresso: about 1:2 by weight (an 18-20 g dose yields roughly 36-40 g of liquid espresso).
- Pour-over / drip / French press: 1:15 to 1:17 is the widely cited "golden ratio" range, with 1:16 as a common middle-ground default. Some sources cite a slightly wider working range of 1:15 to 1:18.
- Cold brew concentrate: roughly 1:8, steeped for 12-24 hours, then typically diluted 1:1 with water or milk before drinking.
Adjusting strength
A lower ratio number (e.g., 1:13) means less water per gram of coffee, producing a stronger, more concentrated cup. A higher ratio number (e.g., 1:18) means more water per gram, producing a milder, more diluted cup. Change the ratio first if you want a stronger or weaker cup; change grind size or brew time only if the cup tastes unbalanced (sour/thin or bitter/harsh) rather than simply weak or strong.
From ratio to your cup size
To brew a specific final volume, work backward: decide how much brewed coffee you want (for example, 350 g/ml for a large mug), then divide by (1 + N) to get the coffee dose, and multiply that dose by N to get the water. For a 1:16 ratio and a 350 g target: dose = 350 / 17 ≈ 20.6 g of coffee, and water = 20.6 × 16 ≈ 329.4 g. This calculator's main mode works from a fixed coffee dose, which is the more common approach since scales measure dose more precisely than a marked water line.