Coffee Ratio Calculator
Calculate how much ground coffee and water you need for any number of cups using your preferred brew ratio.
How to use this tool
- Enter cups of coffee and brew ratio (water:coffee) in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your water and the full breakdown beneath it.
Formula
Water (mL) = Cups × 177.441 (rounded to nearest mL)
Coffee (g) = Water (mL, unrounded) ÷ Brew ratio
Coffee (tbsp) = Coffee (g) ÷ 7
Example at ratio 15:1 and 4 cups: Water = 709.764 mL → 710 mL; Coffee = 709.764 ÷ 15 = 47.32 g; tbsp = 47.32 ÷ 7 = 6.76 tbsp
How it works
The brew ratio expresses how many grams of water are used per gram of ground coffee; a ratio of 15 means 15 g of water for every 1 g of coffee, which sits in the middle of the Specialty Coffee Association's recommended range of 15–18 for filter brewing. The cup volume of 177.441 mL (6 fl oz) is the traditional US “coffee cup” measure, which is smaller than a standard 8 fl oz measuring cup — a distinction that confuses many users. A common mistake is using a 15:1 ratio designed for a drip machine in a French press or pour-over without adjustment, producing under-extracted, watery coffee; espresso uses a far tighter ratio of 1:2 to 1:3.
Worked example
Brewing 4 cups of coffee at a 15:1 ratio
- Calculate water: 4 cups × 177.441 mL = 709.764 mL, rounded to 710 mL.
- Calculate coffee by weight (using unrounded water): 709.764 ÷ 15 = 47.32 g.
- Convert to tablespoons: 47.32 g ÷ 7 g/tbsp = 6.76 tbsp.
710 mL water, 47.32 g ground coffee (approximately 6.76 tbsp)
Common mistakes to avoid
- Using a tablespoon for coffee by volume rather than by weight -- a tablespoon of finely-ground espresso is denser than a tablespoon of coarse French press grind, so volumetric tablespoon measurements produce wildly inconsistent brew strength.
- Applying a drip-coffee ratio (15:1 or 16:1) to espresso -- espresso uses a much lower ratio (typically 1:2 brew ratio by weight output), so using a drip ratio produces a severely under-extracted shot.
- Forgetting that "cups" in coffee makers are often 5-6 fl oz, not 8 fl oz -- a 12-cup coffee maker holds about 60 oz total, not 96 oz; using 8-oz cups in the calculation causes an under-strong brew.
Key terms
- Brew ratio
- The mass of water divided by the mass of ground coffee; a higher number means a weaker, more dilute brew, while a lower number means a stronger, more concentrated brew.
- Coffee cup (US)
- A traditional measure of 6 US fluid ounces (177.44 mL) used in coffee-maker labeling; it is smaller than a standard 8 fl oz measuring cup.
- Extraction
- The process by which hot water dissolves soluble compounds from ground coffee. Under-extraction produces sour, thin coffee; over-extraction produces bitter, harsh coffee.
- Grind size
- The coarseness of ground coffee, which affects extraction rate. Finer grinds extract faster and suit espresso; coarser grinds suit French press and cold brew.
Frequently asked questions
- What is the golden ratio for coffee?
- The Specialty Coffee Association (SCA) recommends 55 g of coffee per litre of water (about 15:1 by weight) as the standard brew ratio for filter coffee.
- How many tablespoons of coffee per cup?
- A rough rule is 1–2 tablespoons of ground coffee per 6 fl oz cup, depending on grind and strength preference. Weight-based measurement (grams) is more accurate.