How to Make Cold Brew Concentrate (Ratio, Dilution, and How Long It Keeps)
One jar of concentrate on Sunday is iced coffee all week — cheaper, smoother, and stronger than anything from a drive-through. Here is the exact ratio, the dilution math, and how long it actually stays good.
Amaya Okonkwo
July 1, 2026
6 min
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Regular cold brew is already the easiest good coffee there is. Concentrate is the smarter version of the same move: brew it strong on purpose, keep a compact jar in the fridge, and dilute each glass to taste in ten seconds. One Sunday batch covers a week of iced coffees for roughly the price of a single café order — and because it's brewed cold and slow, it's smoother and less acidic than any iced coffee you can buy.
The ratio: 1:4 by weight, and why
Cold brew concentrate is a 1:4 ratio — one part coffee to four parts water by weight. In practice: 200 grams of coarsely ground coffee to 800 grams (milliliters) of cold water fills a standard quart-plus jar and yields about 600 ml of concentrate after the grounds drink their share. Ready-to-drink cold brew is closer to 1:8; the whole point of concentrate is brewing at double strength so it survives ice, milk, and a week in the fridge. If you remember one number from this article, it's 1:4.
Our picks, compared
OXO Brew Compact Cold Brew Coffee Maker
Smooth, low-acid concentrate you batch once a week.
County Line Kitchen Mason Jar Cold Brew Maker
Minimalists who want concentrate without another gadget.
Peet's Major Dickason's Blend Whole Bean
Dark-roast lovers and bold French-press cups.
Skip the math — use the coffee ratio calculator
Scaling up for a party pitcher or down for a small jar? The ratio calculator does the gram math for any batch size:
Open the calculator15 g
The method: five minutes of work, twelve hours of waiting
Grind coarse — sea-salt coarse, the same as French press. Combine coffee and cold water, stir until every ground is wet, cover, and leave it: 12 to 18 hours on the counter or in the fridge (fridge steeps run slower, so aim for the long end). Then strain, and strain properly — pour it through the brewer's filter or a fine sieve, and resist squeezing the grounds, which pushes bitterness into an otherwise smooth batch. That's the entire technique. No temperature control, no timing anxiety, no skill ceiling.
The gear question is really a filtration question, because the tedious part of cold brew is the straining. A purpose-built cold brew maker with a built-in filter turns the strain step into lifting out a basket.
Dilution: the part everyone gets wrong
Concentrate is not a drink — pour it straight over ice and you'll wonder why your heart is doing that. Start at one part concentrate to one part water or milk over a full glass of ice, then adjust: 1:1 drinks bold, 1:2 lands near café iced-coffee strength once the ice melts in. For an iced latte, skip the water entirely — concentrate plus cold milk at 1:1.5 is the drive-through drink, minus six dollars. Hot coffee in July, absurdly, also works: 1:2 with just-boiled water.
How long it keeps (and how to tell when it's gone)
Undiluted concentrate keeps 7 to 10 days in a sealed jar in the fridge — the strength that makes it a concentrate also preserves it. Diluted cold brew fades in 2 to 3 days, so store it strong and dilute per glass. It doesn't spoil dramatically; it just goes flat and cardboard-ish. When a batch tastes dull instead of chocolatey, brew the next one — at these coffee quantities a weekly batch costs a few dollars.
Beans matter less here than in any hot method — the cold steep mutes bright, delicate notes anyway — so this is the place for a bold, chocolatey, inexpensive dark roast rather than precious single origins.
- What is the ratio for cold brew concentrate?
- Use 1:4 — one part coarsely ground coffee to four parts cold water by weight. For example, 200 grams of coffee to 800 grams of water yields roughly 600 ml of concentrate after straining. Ready-to-drink cold brew uses about 1:8, so concentrate is simply the same brew at double strength, meant to be diluted per glass.
- How do you dilute cold brew concentrate?
- Start at 1:1 — equal parts concentrate and water or milk over ice — and adjust to taste. One part concentrate to two parts water lands close to café iced-coffee strength once some ice melts. For an iced latte, mix concentrate with cold milk at about 1:1.5 and skip the water.
- How long does cold brew concentrate last in the fridge?
- Seven to ten days in a sealed container, undiluted. Once diluted with water or milk it fades in two to three days, so store the concentrate strong and dilute each glass as you pour. It doesn't spoil so much as go flat — when it tastes dull rather than chocolatey, it's time for a new batch.
- Is cold brew concentrate stronger in caffeine than regular coffee?
- Ounce for ounce, yes — significantly. Brewed at 1:4, undiluted concentrate carries roughly twice the caffeine of regular drip coffee, which is why it's meant to be diluted. Once cut 1:1, a glass lands in the same range as a strong cup of drip, though large or lightly diluted servings can go well beyond it.
Amaya Okonkwo
Amaya is a recipe developer and former café owner who spent six years running a brunch spot's coffee program. She writes about brewing at home without the fuss.