Understanding your brew ratio
The table shows each selectable ratio with its coffee dose per 500 ml and the equivalent grams per liter, compared with the SCA Golden Cup guidance of about 55 g/L ±10%.
| Ratio | Coffee per 500 ml | Grams per liter | Character |
|---|---|---|---|
| 1:15 | 33.3 g | 66.7 g/L | Strong — above the SCA band; suits those who prefer intensity |
| 1:16 | 31.3 g | 62.5 g/L | Balanced — a common filter-brewing starting point, slightly above the SCA band |
| 1:17 | 29.4 g | 58.8 g/L | Moderate — near the upper edge of the SCA band |
| 1:18 | 27.8 g | 55.6 g/L | Light — essentially the SCA 55 g/L reference |
- SCA Golden Cup guidance (~55 g/L ±10%) describes a reference filter brew; personal preference, roast level and brew method legitimately pull recipes outside it.
- Ratio controls strength, but grind size, water temperature and brew time control extraction — the same ratio can taste sour (under-extracted) or bitter (over-extracted) depending on those variables.
- These ratios are for filter and immersion brewing. Espresso uses a much more concentrated convention (commonly around 1:2 beverage weight to dry coffee dose).
- The cups figure uses a 250 ml metric cup; mug sizes vary widely, so measure your actual brew water.
What is a coffee brew ratio?
A coffee brew ratio expresses the proportion of ground coffee to brew water by weight, written as 1:x — one part coffee to x parts water. A 1:16 ratio means 1 g of coffee for every 16 g (≈16 ml) of water, so 500 ml of water takes about 31 g of coffee. Ratio is the primary control over brew strength: lower ratios (1:15) produce a stronger, more concentrated cup, and higher ratios (1:18) a lighter one.
The Specialty Coffee Association (SCA) publishes a widely cited Golden Cup recommendation of approximately 55 g of coffee per liter of water, with an acceptable range of about ±10% (roughly 49-61 g/L). A 1:18 ratio lands almost exactly on that 55 g/L reference, while 1:15 and 1:16 sit somewhat above it in territory many filter-coffee drinkers prefer.
Ratios in this calculator treat milliliters of water and grams of water as equivalent, which is accurate because water weighs very close to 1 g per ml at brewing-relevant temperatures. Weighing both coffee and water on a scale is the most repeatable way to brew.
How to use this coffee ratio calculator
- Enter your brew water volume in milliliters — a standard mug is about 250-350 ml.
- Choose a ratio: 1:15 for a stronger cup, 1:16 as an all-round starting point, 1:17 or 1:18 for a lighter cup.
- Read the coffee dose in grams and weigh it out; the calculator also shows the grams-per-liter figure to compare against SCA guidance.
- Taste and adjust one step at a time — if the cup is too intense, move to a higher ratio; if weak or sour, try a lower ratio or a finer grind.
The formula behind the coffee dose
The coffee dose is the water weight divided by the ratio number. The grams-per-liter figure is the dose divided by the water volume in liters, which lets you compare any recipe against the SCA's ≈55 g/L Golden Cup guidance.
Worked example: 500 ml of water at 1:16 needs 500 ÷ 16 = 31.3 g of coffee. That is 31.3 ÷ 0.5 = 62.5 g per liter — above the SCA's 55 g/L center point, within the stronger end many filter drinkers prefer. At 1:18, 1000 ml of water takes 1000 ÷ 18 = 55.6 g, almost exactly the SCA reference.
Common mistakes
- Measuring coffee by scoops or tablespoons — bean density varies by roast and origin, so a scoop can swing several grams; weigh the dose instead.
- Fixing a bitter or sour cup by changing the ratio only — bitterness usually signals over-extraction (grind coarser or shorten the brew) and sourness under-extraction, not just the wrong dose.
- Confusing filter ratios with espresso ratios — 1:16 is a filter convention; espresso is typically expressed around 1:2 beverage weight to dry dose.
- Ignoring the water retained by the grounds — spent grounds hold roughly twice their weight in water, so the beverage yield is less than the water poured.
- Changing several variables at once — adjust ratio, grind or temperature one step at a time to learn what each does.
よくある質問
How much coffee do I need for 500 ml of water?
At the common 1:16 ratio, 500 ml of water takes 500 ÷ 16 = 31.3 g of ground coffee. At 1:15 it is 33.3 g, at 1:17 it is 29.4 g, and at 1:18 it is 27.8 g. Weigh the coffee on a digital scale rather than using scoops, because bean density varies by roast.
What is the SCA Golden Cup standard?
The Specialty Coffee Association's Golden Cup guidance recommends brewing with approximately 55 g of coffee per liter of water, with an acceptable range of about ±10% (roughly 49-61 g/L). A 1:18 ratio lands almost exactly on 55 g/L; 1:15-1:16 sits somewhat above it for those who prefer a stronger cup.
What is the best coffee-to-water ratio?
There is no single best ratio — it is a preference dial. A 1:16 ratio (about 62.5 g/L) is a widely used starting point for pour-over and drip brewing. Move toward 1:15 for a stronger cup or toward 1:18 (about 55.6 g/L, essentially the SCA reference) for a lighter one, changing one step at a time and tasting.
Do milliliters of water and grams of water mean the same thing here?
Effectively yes. Water weighs very close to 1 g per ml at the temperatures relevant to brewing, so a 1:16 ratio can be treated as 1 g of coffee per 16 ml of water. For maximum repeatability, brew on a scale and weigh the water in grams.
Does this ratio work for espresso or cold brew?
No — these are filter and immersion ratios. Espresso is conventionally expressed far more concentrated, around 1:2 beverage weight to dry coffee dose. Cold-brew concentrate typically uses much lower ratios too (often around 1:5 to 1:8) and is diluted before drinking. Use method-specific recipes for those styles.
Why does my coffee taste weak even at a strong ratio?
Strength also depends on extraction, not just dose. A too-coarse grind, water well below the commonly recommended 90-96 °C brewing range, or a too-short contact time under-extracts the grounds, producing a weak or sour cup even at 1:15. Grind finer or extend the brew time before adding more coffee.
参考文献
- Specialty Coffee Association. Golden Cup Standard — coffee-to-water proportion guidance (≈55 g/L ±10%). sca.coffee.
- Specialty Coffee Association. Coffee Standards — brewing water temperature and practice. sca.coffee.
- Lingle, T. The Coffee Brewing Handbook. Specialty Coffee Association of America (1996).