Coffee ratios are the difference between a watery disappointment and a bitter disaster. Here's the exact ratio for every method, plus the simple maths to scale it to any cup size.
The single biggest variable in home coffee quality isn't the beans or the equipment — it's the ratio. Most people eyeball it, and most people's coffee suffers for it. Here's the precise maths for every brewing method.
The Specialty Coffee Association (SCA) recommends a baseline ratio of 1:15 to 1:17 (coffee to water by weight). This means for every gram of coffee, you use 15–17 grams of water.
Note: always measure by weight (grams), not volume (tablespoons or scoops). Coffee density varies dramatically between roasts and grind sizes, making volume measurements unreliable.
Espresso uses a different measurement system — the brew ratio — which compares the weight of dry coffee going in to the weight of liquid espresso coming out.
Good espresso extraction typically takes 25–30 seconds. If it runs faster, the grind is too coarse; slower means too fine. Adjust grind size before adjusting dose.
If your coffee tastes bitter or harsh: try a slightly higher ratio (more water, e.g. 1:17 instead of 1:15). Bitterness often indicates over-extraction — the water is pulling too many compounds from the grounds.
If your coffee tastes weak, sour, or watery: try a slightly lower ratio (less water, e.g. 1:14). Sourness often indicates under-extraction — the water hasn't pulled enough from the grounds.
Change only one variable at a time. Ratio and grind size affect extraction in similar ways — if you adjust both simultaneously, you won't know which change caused the improvement.
The SCA recommends brewing temperature of 91–96°C (196–205°F). Boiling water (100°C) over-extracts and creates bitterness. Water cooler than 88°C under-extracts. If you don't have a thermometer, boiling water left to rest for 30–45 seconds in a kettle typically drops to the right range.
Exception: cold brew is brewed at room temperature or refrigerator temperature over 12–24 hours. The low temperature slows extraction, which is why the ratio is much higher and the time much longer.