Cold Brew Ratio: How Much Coffee per Cup of Water

Cold brew is forgiving, which is why it is the easiest way to make good coffee at home. But the ratio of coffee to water decides almost everything about the glass you end up with: how strong it tastes, how long it keeps, and whether you need to dilute it.

Method

Cold brew concentrate

Ratio1:5

Coffee

100 g

Water

500 ml

Grind

Coarse, like sea salt

Water temp

Room temp or fridge

Time

16–20 h

Why ratio matters more than time

Cold water extracts coffee slowly and fairly evenly, so after the first twelve hours or so the brew changes less than you might think. The ratio, on the other hand, sets the ceiling: there is only so much flavour a given amount of grounds can give to a given amount of water.

That is why weighing beats scooping. A "cup" of coarse grounds can weigh anything from 70 to 100 grams depending on the roast and grind, which is the difference between a pleasant drink and a muddy one.

Concentrate or ready to drink?

Concentrate (1:4 to 1:5) takes up less space in the fridge and keeps a little better. You decide strength at serving time, which suits households where one person wants it black and another wants it with lots of milk.

Ready to drink (1:8 to 1:10) skips the dilution step. It is what most cafés pour, and it is the better choice if you drink it straight over ice.

Cold brew ratio chart

Batch	Coffee	Water	Ratio	Serve
Strong concentrate	125 g	500 ml	1:4	Dilute 1:2
Concentrate	100 g	500 ml	1:5	Dilute 1:1
Ready to drink	60 g	500 ml	1:8	Straight over ice
Light	50 g	500 ml	1:10	Straight

Grind size and steep time

Use a coarse grind, roughly the texture of sea salt. Finer grounds extract faster but clog the filter and leave a silty, bitter cup. If your grinder has numbered settings, start near the coarsest end and move one step finer if the result tastes weak.

At room temperature, 14 to 18 hours is the sweet spot. In the fridge extraction is slower, so give it 18 to 24 hours.

Fixing a batch that went wrong

• Weak or watery: use more coffee next time (move from 1:8 toward 1:6) before you try a finer grind.
• Bitter or harsh: the grind is probably too fine, or it steeped past 24 hours.
• Sour or thin: steep longer, or let it sit at room temperature instead of in the fridge.
• Cloudy or gritty: filter a second time through a paper filter.

How long does it keep?

Strained and sealed in the fridge, concentrate stays good for about a week and ready-to-drink cold brew for four or five days. After that it flattens out and picks up fridge flavours, even if it is still safe.