Cold Brew Calculator

In short Cold brew is made as a concentrate and then diluted, and both stages have arithmetic worth doing. The first surprise is that a 1:5 batch does not give you five parts of coffee. The grounds keep roughly twice their own dry weight in water and never give it back, so 200 g of coffee steeped in 1,000 g of water yields about 600 g of concentrate rather than 1,000. Recipes almost never mention this, and it is the reason a batch always looks short. Squeezing the bag recovers some of it, along with a good deal of silt. The second stage is a mixing problem with an exact answer, because DILUTION CREATES NOTHING. The dissolved solids are fixed the moment the steep ends, so strength times weight is the same before and after: 4% of 600 g is 24 g of solids, and after dilution it is 1.25% of 1,920 g, which is the same 24 g. That single identity gives you the water for any target strength in one division, in either direction. And ice counts as water — a full glass adds 100 to 150 g by the time you reach the bottom, which is most of a dilution on its own. THE THING WORTH UNDERSTANDING is that cold brew concentrate is strong and under-extracted at the same time, and those are not contradictory. Strength is solids per gram of liquid; extraction is solids per gram of coffee. The example above works out at around 12% extraction, well under the 18 to 22% a filter brew aims at, and that is normal rather than a fault: cold water dissolves the same compounds far more slowly, and even twelve hours does not fully make up for eighty degrees of missing heat. Cold brew gets its strength from using four times the coffee, not from pulling more out of it — which is why it costs more per cup and why the flavour is genuinely different rather than merely milder. Much of the acidity is simply never dissolved. On timing: twelve to eighteen hours at room temperature, or sixteen to twenty-four in the fridge. Past about a day the returns are small and the risk is not, so brew cold if you are going long, and drink it within a week.