Cold brew concentrate is one of the least expensive and most satisfying things you can make at home. There is no need to buy a single-purpose gadget when something you likely already own works even better. For making cold brew concentrate at home, a French Press is hard to beat.
What You'll Need
- A French Press of at least 34 oz. is ideal. If you don't have one, a mason jar or any properly sized food-safe container will work. We'll call it the brewing vessel from here on out.
- Coffee: 142g (5 oz.), medium-dark roast, coarsely ground to roughly the texture of sea salt.
- Water: 850g (30 oz.), cool and fresh. Filtered water makes a noticeable difference. See our post on water for coffee brewing for more detail.
- A silicone spatula or spoon for stirring during the steep.
- A gram scale. This matters more than you might think. See below.
Why Weight Measurements Matter Here
The cold brew concentrate ratio is 1:6 by weight, one part coffee to six parts water. That's it. Use a scale and measure both the coffee and the water in grams. Do not use volume measurements like cups, ounces, or scoops. Those are volume, not weight, and volume measurements are unreliable for coffee because grind size and roast level both affect how much a given scoop actually weighs.
If your brewing vessel holds more or less than 34 oz., the ratio adjusts automatically. For a larger batch, 300g of coffee to 1800g of water is the same 1:6 ratio scaled up. For a smaller vessel, just divide accordingly. The math always works the same way.
Cold Brew Concentrate at a Glance
Coffee: 142g, medium-dark roast, coarsely ground
Water: 850g, cool and filtered
Ratio: 1:6 by weight
Steep time: 18 hours at room temperature
The Brewing Process
Start 18 hours before the time you want to finish. Starting at 4:00 PM and filtering at 10:00 AM the next morning is a reliable rhythm.
- Add the coffee grounds to the brewing vessel first, then add the water. Starting with grounds and adding water helps ensure everything gets saturated from the beginning. Stir well to make sure all the grounds are fully wet.
- Stir periodically, roughly every ten minutes, until the grounds are fully saturated. You'll know you're there when no floating cake of dry grounds remains at the top of the vessel.
- After the final stir, cover the vessel with a lid and let the mixture steep at room temperature for 18 hours. Cold brew gets its name from the fact that no hot water is used, not from steeping in the refrigerator. Keep it at room temperature during the steep. If you prefer to steep in the refrigerator, extend the time to a full 24 hours to compensate for the slower extraction at lower temperatures.
Separating the Concentrate
After 18 hours, all that remains is separating the grounds from the liquid.
- If you used a French Press, gently press the plunger all the way down to trap the grounds at the bottom. Pour the concentrate into a sealed container and refrigerate. This should yield about 26 to 28 ounces of cold brew concentrate. Some water is absorbed by the grounds during steeping, which is normal.
- If you used a mason jar or other vessel, strain the grounds through the metal or paper filter from your drip coffee machine. It takes a little longer but the result is equally good.
Serving Your Cold Brew Concentrate
What you've just made is a concentrate, not a ready-to-drink beverage. Dilute it before serving. Start with a 1:2 ratio of concentrate to water and adjust to taste from there. Cold brew is best served over ice.
A useful way to think about it: for every 1 ounce of cold brew concentrate, you end up with 3 ounces of ready-to-drink cold brew after dilution. Substitute cold milk for the water when diluting for an easy cold brew latte.
Storage
Cold brew concentrate stays fresh and tasty in a sealed container in the refrigerator for at least 21 days. It has been tested to 34 days with no noticeable loss in quality, so there is no need to rush through it.
A Note on the Coffee You Use
Cold brew is forgiving but not indifferent to coffee quality. A medium-dark roast with good body works best. Fresh coffee makes a meaningful difference even in cold brew, where the long steep might seem to level the playing field. For more on freshness and why it matters, see our guide on how to keep coffee fresh. And if you want an even faster cold brew option that's ready in two minutes rather than 18 hours, see the cold brew method in our AeroPress Brewing Guide.
Cold brew trades temperature for time, but the same underlying variables still apply. For a full look at how grind, ratio, time, and water quality shape any cup, see our guide to coffee brewing variables.
Frequently Asked Questions About Cold Brew Coffee
What is the coffee-to-water ratio for cold brew?
Cold brew concentrate uses approximately a 1:6 ratio by weight, which is much stronger than hot brewing methods because the concentrate is diluted before serving. Measure by weight rather than volume for consistent results.
How long should cold brew steep?
Twelve to eighteen hours is the typical range. Shorter steeps produce a lighter, more delicate concentrate. Longer steeps produce more body and intensity. Beyond about twenty-four hours the coffee can turn woody and flat.
What grind size is best for cold brew?
Coarse, similar to what you would use for a French Press. Cold water extracts far more slowly than hot water, and a coarse grind prevents the fines from over-extracting during the long steep and makes filtering much easier.
Do I need to refrigerate cold brew while it steeps?
Either works. Room-temperature steeping extracts slightly faster, so you may want to shorten the steep time. Refrigerated steeping is slower and more forgiving. Once separated from the grounds, always refrigerate the concentrate.
How long does cold brew concentrate last?
Properly refrigerated cold brew concentrate stays good for about two weeks. The flavor is best in the first week. Because there are no grounds left in contact with the liquid, it does not continue extracting in storage.
Why does my cold brew taste weak?
Weak cold brew usually means the ratio was too dilute, the steep was too short, or the grind was too coarse for the steep time used. Cold water is a much less efficient solvent than hot water, so cold brew needs both a stronger ratio and far more time.
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