How this instrument works
Coffee strength comes down to one number that matters more than grind size, water temperature, or bean origin: how much water passes through how much coffee. The Specialty Coffee Association's Golden Cup guidance anchors this around roughly 55 grams of coffee per litre of water — close to a 1:18 ratio by weight — as the starting point most brewers find balanced across drip, pour-over, and other hot-brew methods, with individual taste and roast level nudging the exact figure up or down.
This instrument uses a 1:17 ratio, a slightly stronger, easy-to-remember round number that sits inside the range specialty coffee guidance treats as balanced (roughly 1:15 to 1:18 depending on roast and method) and is simple to scale by hand: 20 g of coffee calls for 340 mL of water without needing a calculator at the counter.
Because both sides scale together, the ratio holds true whether you're brewing a single 15 g cup or a 60 g carafe for a full pot — the strength of the cup stays the same, only the total volume changes, which is what makes a fixed ratio more useful day-to-day than memorizing water amounts for a handful of specific cup sizes.
- Enter the coffee dose in Coffee (g) — weigh your grounds on a kitchen scale for consistent results.
- Read Water (mL) — the amount of water to use, at a 1:17 ratio by weight.
- Brew with filtered water between roughly 195-205°F (90-96°C) for the ratio to translate into a well-balanced cup.
- Taste and adjust — a 1:17 ratio is a solid starting point, not a rule; move toward 1:15 for a stronger cup or 1:18 for a lighter one.
Worked example — 20 g of coffee for a single pour-over
A pour-over brewer weighs out 20 g of medium-roast coffee for a single large cup. At the 1:17 ratio, water needed = 20 × 17 = 340 mL.
340 mL of water through 20 g of coffee lands squarely inside the range specialty coffee guidance treats as a balanced hot brew — strong enough to carry flavor clearly without tasting thin, and dilute enough to avoid the bitterness that comes from over-extracting a smaller water volume through the same amount of grounds.
Questions
Is 1:17 the official SCA Golden Cup ratio?
Not exactly — the SCA's published Golden Cup guidance centers on roughly 55 g of coffee per litre of water, which works out closer to 1:18, within a stated range that's commonly described as 1:15 to 1:18 depending on roast level and brew method. This calculator uses 1:17 as a simple, easy-to-scale round number that sits comfortably inside that specialty-coffee-standard range rather than claiming to be the exact SCA figure.
Why does a stronger ratio like 1:15 taste different from 1:18?
A lower ratio number means less water relative to coffee, concentrating more dissolved coffee solids into the same cup — the result reads as bolder and heavier-bodied. Pushing toward 1:18 or beyond spreads the same coffee dose across more water, producing a lighter, more tea-like cup that lets delicate flavor notes come through more clearly but can taste thin if pushed too far.
Does this ratio work for espresso too?
No — espresso uses a fundamentally different, much more concentrated ratio, typically around 1:2, because it's a pressurized, fast extraction rather than a gravity-fed hot brew. This 1:17 ratio is meant for drip, pour-over, French press, and similar hot-brewing methods where water passes through the grounds over one to five minutes.
Should I use this same ratio for cold brew?
No — cold brew uses a much lower, more concentrated water ratio (commonly around 1:4 for a concentrate meant to be diluted, or 1:8 for a ready-to-drink batch) because cold water extracts far less efficiently than hot water over the same steeping time. This site's cold brew ratio calculator uses those cold-brew-specific figures rather than the hot-brew ratio here.
Does grind size change the water ratio I should use?
Not directly — the ratio is about total water versus total coffee, while grind size controls how fast that water extracts flavor as it passes through. A finer grind extracts faster and can taste over-extracted or bitter at the same ratio and brew time a coarser grind handles well, so grind size is usually the first thing to adjust before changing the ratio itself.