Getting the ratio of coffee to water right is the single biggest variable under your control when brewing at home. Too little coffee and you get a thin, sour, under-extracted cup; too much and it turns bitter and harsh. This calculator applies the standard ratios used by specialty-coffee professionals to give you an exact recipe for every major brew method — from a morning pour-over to a cold-brew concentrate.
How the ratio works
The coffee-to-water ratio is expressed as 1 : X, where 1 is one part coffee by weight and X is the number of parts water by weight. Because 1 ml of water weighs approximately 1 gram, you can treat grams and millilitres interchangeably for the water side.
The core formula is straightforward:
- Water needed (given coffee) = coffee grams / ratio fraction
- Coffee needed (given water) = water grams × ratio fraction
For example, at a 1:15 ratio:
- 15 g of coffee → 15 / (1/15) = 225 ml of water
- 300 ml of water → 300 × (1/15) = 20 g of coffee
The ratio fraction here is 1/15 = 0.0667 (grams of coffee per gram of water).
Brew method ratios at a glance
Different methods extract at different rates and produce different concentrations, so each has its own “sweet spot”:
| Method | Recommended range | Typical grind | Water temp |
|---|---|---|---|
| Pour-over (V60, Chemex) | 1:12 – 1:18 | Medium-fine | 93 °C |
| French press | 1:11 – 1:17 | Coarse | 93 °C |
| AeroPress | 1:8 – 1:18 | Medium-fine to fine | 80 °C |
| Espresso | 1:1.5 – 1:2.5 | Very fine | 93 °C |
| Cold brew | 1:5 – 1:9 | Coarse | Cold (4–20 °C) |
| Moka pot | 1:6 – 1:10 | Fine | 90 °C |
| Drip / filter machine | 1:13 – 1:18 | Medium | 93 °C |
Worked example — pour-over for two people
Suppose you want two 200 ml cups using a Hario V60 at a balanced 1:15 ratio:
- Total water = 2 × 200 = 400 ml
- Coffee needed = 400 × (1/15) = 26.7 g (round to 27 g)
- Bloom water = 27 × 2 = 54 g — pour this first, wait 35 seconds
- Remaining water = 400 − 54 = 346 g — pour in two or three controlled pours
- Total brew time: approximately 3 minutes 30 seconds
Result: a clean, bright cup sitting right in the SCA’s recommended extraction window.
The SCA “golden ratio”
The Specialty Coffee Association’s standard for brewed coffee calls for 55 g of coffee per litre of water — a 1:18.2 ratio. This is a baseline, not a rule. Light-roast coffees often taste better slightly stronger (1:15) because their acidity is pronounced; dark roasts can go lighter (1:17–1:18) without losing body. Treat the golden ratio as the midpoint of a spectrum, not a target to hit exactly.
Espresso: a different world
Espresso ratios refer to the brew ratio — the weight of dry grounds versus the weight of liquid espresso (the “yield”). A 1:2 ratio means 18 g of ground coffee produces 36 g of espresso in the cup. This is measured by placing the cup on a scale during extraction. The volume of a shot (roughly 30 ml for a double) is not the same as the yield weight because crema adds volume without proportional mass. Always weigh espresso output for accuracy.
Tips for dialling in
- Start with the balanced preset for your method, taste, then adjust.
- Grind size and ratio interact — if you make the grind coarser (faster flow, less extraction), compensate by using slightly more coffee.
- Water quality matters — filtered water with moderate mineral content (around 150 ppm TDS) extracts more evenly than very soft or very hard water.
- Scale beats scoops — a 0.1 g kitchen scale removes all guesswork; a tablespoon varies by 20–30% depending on how it is scooped.
- Keep a brew log — note ratio, grind setting, and your tasting notes; tiny adjustments compound into a much better cup over a few sessions.