Coffee-to-water ratio calculator
Weigh the water, divide by the second number of the ratio, and you have the grams of coffee. The boxes above do that division; the table and the pitfalls are below.
12 × 12 = 144
Adding 12 to itself 12 times gives the same answer.
The arithmetic
Coffee in grams = water in grams ÷ the ratio number. At 1:16 with 500 g of water, that is 500 ÷ 16 = 31.3 g of coffee. Going the other way, water = coffee × the ratio number, so 20 g of coffee at 1:15 wants 300 g of water.
Water weighs the same as its volume in millilitres, so 500 ml is 500 g. That equivalence is what lets one number serve both a jug and a scale.
| Ratio | Coffee for 500 g water | Water for 20 g coffee |
|---|---|---|
| 1:14 | 35.7 g | 280 g |
| 1:15 | 33.3 g | 300 g |
| 1:16 | 31.3 g | 320 g |
| 1:17 | 29.4 g | 340 g |
| 1:18 | 27.8 g | 360 g |
Reading the result
A smaller second number means more coffee per unit of water and a stronger cup; a larger one means a lighter cup. The ratio is a starting point you adjust by taste, and grind size and brew time change the outcome just as much as the numbers do.
Where it goes wrong
- Scoops instead of grams. A scoop of one roast and a scoop of another do not weigh the same. Weigh the beans if you want the ratio to mean anything.
- The machine’s “cup”. The cup marks on a drip brewer are rarely 250 ml. Check what yours actually holds before you scale a recipe to it.
- Brewed volume, not water added. The grounds keep some of the water. Base the ratio on the water you pour in.
- Ratio written backwards. 16:1 would be sixteen parts coffee. Coffee is always the 1.
To scale a ratio up or down cleanly, use the equivalent ratio calculator, or the ratio calculator for 3 numbers when a third ingredient joins in. More on the calculators page.