Cold Brew Concentrate Calculator

Cold brew works because solubility and reaction rates are strongly temperature dependent. Water at 4 to 20 degrees C dissolves coffee solids far more slowly and more selectively than water at 93 degrees C, so extraction needs 12 to 24 hours instead of four minutes, and compounds that require heat to mobilize, including many bitter degradation products and much of the coffee oil, transfer in smaller proportion. That selectivity, not a large pH shift, is why it tastes sweeter; measured pH near 5.0 to 6.0 is only modestly above hot coffee, so the low-acid claim concerns perceived acidity. Ratios by weight run 1:4 to 1:5 for a concentrate meant to be cut one to one or one to two, 1:8 for full strength, and 1:12 to 1:15 for something drinkable straight over ice. Batch math must account for absorption: grounds keep roughly 2 g of liquid per gram of dry coffee. The 0.85 yield factor represents that loss, which is why a 64 oz target requires brewing closer to 75 oz. At about 6 mg of caffeine recovered per gram of dry coffee, a 1:5 concentrate lands near 200 to 300 mg per 8 oz before dilution, against roughly 95 mg for drip coffee, and the FDA cites 400 mg per day as a level not generally associated with adverse effects in healthy adults. Coarse grinding keeps fines from over-extracting and clogging filtration. Concentrate keeps about 10 to 14 days refrigerated and diluted brew only 3 to 5, while room-temperature steeping runs several hours faster than fridge steeping.

Extracting coffee without heat is an old and geographically scattered idea rather than a single invention. Kyoto-style slow drip, in which cold water descends through a bed of grounds one drop at a time over several hours, is a long-standing Japanese practice often linked to Dutch trade contact during the Edo period, though the documentary trail for that origin story is thin. A better-documented nineteenth century case is the mazagran of French Algeria, where troops were supplied with a coffee syrup or concentrate to be mixed with cold water, which is functionally the same product this calculator describes. The modern American version has a clear starting point. Todd Simpson, a chemical engineering graduate who encountered a cold water extraction method while travelling in Latin America, developed the Toddy Cold Brew System and brought it to market in 1964, promoting it specifically on reduced acidity for drinkers whose stomachs objected to hot coffee. It remained a small niche for roughly four decades, kept alive by home users and a few cafes. The commercial breakout is recent and rapid: specialty roasters began bottling cold brew around 2011, with Stumptown's stubby-bottle release among the most visible, and Starbucks rolled cold brew out across its United States stores in 2015. That expansion is what pushed concentrate ratios, steep times and dilution rates from informal shop knowledge into written recipes and calculators.