Coffee ratio calculator
Coffee grounds retain roughly two grams of water for every gram of coffee. Brew 500 g of water with 30 g of coffee and about 60 g stays in the filter, so you pour around 440 ml rather than 500. For a single cup it is a rounding error; for a carafe you meant to fill exactly, it is why it comes up short.
Brew ratios are stated by weight: 1:16 means one gram of coffee to sixteen of water. Five hundred grams of water at 1:16 needs 31 g of coffee, and an 18 g dose at the same ratio wants 288 g of water. Solve it either way round; stronger sits around 1:15, lighter around 1:17.
How to use a brew ratio
Ratio sets strength, but grind size sets extraction, and confusing the two is why adjustments so often fail. A brew that tastes thin and sour is under-extracted and wants a finer grind or a longer time, not more coffee; adding coffee to a sour brew only gives you a stronger sour brew. One that tastes harsh and bitter is over-extracted and wants a coarser grind. Change one variable at a time, and change the grind before the ratio.
Two other things move the result and neither is on the dial. Temperature comes first: most filter methods want water between 90 and 96 °C, which is a kettle left off the boil for about thirty seconds. Then the water itself. Distilled water extracts badly because minerals take part in extraction, very hard water over-extracts and scales the kettle, and roughly 75 to 150 ppm of dissolved solids sits in the middle. It is why some cafés filter their water and then deliberately put minerals back.
Whichever direction you solve in, the grounds keep about two grams of water for every gram of coffee. What you pour is always less than what you weighed: an 18 g dose at 1:16 takes 288 g of water and gives back roughly 252 ml in the cup.
What people use it for
- Scaling a recipe from one cup to a carafe
- Working out the water for a dose you have already weighed
- Dialling in a pour-over
- Setting up a French press
- Sizing a travel brew around the beans you packed
- Comparing brew ratios between methods
Questions
1:16 by weight is the common starting point. 1:15 is stronger, 1:17 lighter.
About 15 g for a 240 ml cup at 1:16. Two tablespoons is roughly 10 g, which is why spoon measures run weak.
320 g at 1:16, or 300 g at 1:15 for something stronger.
Near enough: one millilitre of water weighs one gram at room temperature, so a scale can replace a jug.
Weigh. Bean density varies with roast, so a scoop of light roast weighs noticeably more than a scoop of dark.
The grounds retain about two grams per gram of coffee. Twenty grams of coffee keeps roughly 40 ml back in the filter.
Under-extraction. Grind finer or brew longer rather than adding more coffee.
Somewhat. Espresso runs about 1:2, cold brew concentrate 1:5 to 1:8, and filter methods around 1:16.
Sixty grams to a litre is the usual reference, which is 1:16.7. A three-cup pot holds about 350 g of water, so 21 g of coffee.
Between 90 and 96 °C for most filter methods. Off the boil for thirty seconds is close enough without a thermometer.
Considerably. Distilled water extracts poorly and very hard water over-extracts; around 75–150 ppm of dissolved minerals is the target range.
Ground coffee runs about 5 g to a level tablespoon, so an 18 g dose is between three and four. The tool prints the figure so you can check a scoop against it.