Start cold brew at 1 part coffee to 15 parts water by weight if you want to drink it straight. For a concentrate, start at 1:8, then dilute the finished brew to taste. Those are starting lines, not laws carved into a tiny coffee tablet.
Our house method is reassuringly uneventful: coarse coffee, cool water, a covered container, and 24 hours in the refrigerator. Strain it thoroughly and keep it cold.
- Ready to drink
- 1:15 — 67 g coffee for 1,000 g water
- Concentrate
- 1:8 — 125 g coffee for 1,000 g water
- Grind
- Coarse, then adjust by taste
- Steep
- 24 hours, covered and refrigerated
The calculator, without the calculator
Divide the water weight by the second number in the ratio. For 750 grams of water at 1:15, that is 750 ÷ 15, or 50 grams of coffee. At 1:8, the same water takes about 94 grams.
A kitchen scale makes this much easier because one millilitre of water weighs almost exactly one gram for coffee-making purposes. Weigh the water and skip the measuring-jug philosophy seminar.
Ready to drink or concentrate?
Ready-to-drink cold brew is simpler: strain it and pour it. Concentrate uses more coffee but leaves room for ice, milk, or water. A one-to-one mix of concentrate and water is a sensible first glass, not a required dilution. Taste it before adding anything else.
If it is heavy or drying, add water first. If it is thin, use less dilution next time—or brew a stronger batch. Change one thing at a time, because changing ratio, grind, steep time, and your entire personality makes the result hard to diagnose.
Grind and strain
Coarse is a useful starting point because it is easier to filter and less likely to leave a silty cup. Your grinder’s number is not universal, so use the particles—not somebody else’s dial—as your reference. Our grind-size guide has the useful comparisons.
Pour through a fine mesh, then through paper if you want a cleaner cup. Do not squeeze the grounds; pressure pushes more fine material into the drink and rarely improves anybody’s afternoon.
Keep the cold part cold
Brew in a clean, covered, food-safe container and refrigerate at 40°F / 4°C or below. Make small batches, keep the finished coffee covered, and discard it if its smell, appearance, or handling gives you reason to doubt it. Home-brew advice should not be stretched into a claim about the shelf life of sealed commercial coffee.
Want the story before the arithmetic? Start with our two-ingredient method, then see why cold brew and iced coffee are not the same drink.
Sources & further reading
- National Coffee Association — Cold Brew Resource CenterIndustry food-safety and handling resources for cold-brew coffee.
- U.S. FDA — Refrigerator Thermometers: Cold Facts about Food SafetyThe basis for the 40°F / 4°C refrigerator guidance.
- Rao & Fuller — Acidity and antioxidant activity of hot and cold brew coffeePeer-reviewed comparison of pH, titratable acidity, and antioxidant activity.