Cold Brew Ratio Calculator

Cold brew replaces heat with time. The solubility of most coffee compounds rises sharply with temperature, so water at 20 degrees C, or 4 degrees C in a refrigerator, dissolves them far more slowly than water at 95 degrees C. Extending contact time from four minutes to 12 to 24 hours compensates. The exchange is not neutral: several bitter and aromatic compounds that dissolve readily in hot water, including some of the chlorogenic acid degradation products responsible for harshness, are extracted much less efficiently at low temperature, which is why cold brew tastes rounder and sweeter. It is worth noting that this is a flavour difference rather than a pH difference; laboratory comparisons of the same coffee brewed hot and cold generally land at similar acidity, near pH 5. The arithmetic in this calculator has two parts. The ratio of water to coffee sets strength: roughly 1 to 4 through 1 to 6 by weight for a concentrate meant to be diluted, 1 to 8 for a strong ready pour, and 1 to 12 through 1 to 16 for a brew drunk straight. Yield is then reduced by retention, because saturated grounds hold about twice their own dry weight in liquid, so 100 g of coffee in 500 ml of water returns near 300 ml rather than 500 ml. Grind must be coarse, similar to raw sugar, both to avoid over-extraction across a long steep and to keep fines out of the filter. Practical limits: below about 12 hours the brew is thin and sour, beyond 24 hours it turns woody and astringent, and concentrate keeps its character for roughly 7 to 10 days in a sealed refrigerated container. Caffeine estimates near 6 mg per gram of grounds are approximate and vary with bean species and grind.

Steeping coffee in cool water is old and geographically scattered. The best documented early tradition is Japanese, where Kyoto-style or Kyoto drip towers, tall glass rigs that let cold water fall through a bed of grounds one drop at a time over several hours, have been used in Japanese coffee houses since at least the nineteenth century. The often repeated claim that Dutch traders carried the technique to Japan is popular but poorly evidenced, and is better treated as an origin story than as history. The modern immersion method has a clearer paper trail. In 1964 Todd Simpson, a chemical engineering graduate of Cornell University, patented and began selling the Toddy Cold Brew System after encountering a cold water coffee preparation while travelling in Latin America. His design was deliberately simple: a bucket, a felt filter, a long room-temperature steep, and a concentrate that could be diluted to taste. For decades it remained a niche product sold mainly to people who found hot brewed coffee too acidic. Cold brew moved into the mainstream only in the 2010s, when specialty roasters began bottling it and large chains adopted it; Starbucks added cold brew across its United States stores in 2015 and introduced nitrogen-infused cold brew the following year. That commercial wave is also what pushed ratio and steep-time guidance from cafe folklore toward the published, weight-based recipes used today.