Cold Brew Concentrate: How to Make It and Get the Dilution Right
One batch, a week of coffee. Here's how to brew cold brew concentrate at home and dilute it so every glass tastes like the café version.
Why Brew a Concentrate Instead of Ready-to-Drink Cold Brew?
Most home cold brew recipes make a jug of coffee you drink as-is. That works, but it eats fridge space and it locks you into one strength. Cold brew concentrate flips the model: you brew a small, intense batch once, then dilute each glass to taste. One 1-litre jar of concentrate becomes three to four litres of iced coffee, or a week of iced lattes.
Concentrate also keeps better. With less water and a higher dissolved-solids content, it stays bright and sweet in the fridge for about two weeks, while diluted cold brew starts tasting flat after four or five days.
The Ratio That Actually Matters
There are two ratios in cold brew, and mixing them up is the single most common reason home batches taste weak or harsh.
- Brew ratio — coffee to water in the jar. For concentrate, use 1:5 by weight (200 g coffee to 1,000 g water). For a gentler concentrate, go 1:6.
- Dilution ratio — concentrate to water or milk in the glass. Start at 1:2 (one part concentrate, two parts liquid) and adjust.
Weigh both. Volume measurements for coffee vary by up to 20% depending on how coarse the grind is and how the grounds settle, and at 1:5 that error is the difference between syrupy and thin.
| Batch size | Coffee | Water | Yields (diluted 1:2) |
|---|---|---|---|
| Small | 100 g | 500 ml | ~1.5 L |
| Standard | 200 g | 1,000 ml | ~3 L |
| Big week | 300 g | 1,500 ml | ~4.5 L |
Step by Step
1. Grind coarse — but not too coarse
Aim for a grind slightly coarser than French press: chunky, like raw sugar. Too fine and the long steep pulls bitter, dusty flavours plus a sludge you'll never fully filter out. Too coarse and 16 hours won't be enough to extract sweetness.
2. Combine and stir
Add grounds to a large jar, pour in room-temperature filtered water, and stir until every ground is wet. Dry pockets floating on top are dead weight — they contribute nothing but volume.
3. Steep 16–20 hours
Room temperature for 16 hours, or the fridge for 20–24. Room-temperature steeping extracts faster and gives a rounder, sweeter cup; fridge steeping is cleaner and more delicate. Past 24 hours you gain little except woody, papery notes.
4. Filter twice
Strain through a fine mesh sieve first to catch the bulk, then through a paper filter or a clean cloth to remove fines. Don't squeeze the grounds — you'll push bitter silt straight into your finished concentrate.
5. Store
A sealed glass bottle in the fridge. Label it with the date. Two weeks is the practical limit for peak flavour.
Diluting Like a Barista
- Iced coffee: 1 part concentrate, 2 parts cold water, over plenty of ice.
- Iced latte: 1 part concentrate, 2 parts milk. Oat milk holds up best against the intensity.
- Hot cold brew: 1 part concentrate, 2 parts hot water. Smooth and low-acid — good if regular coffee upsets your stomach.
- Espresso substitute: undiluted, 30–45 ml as the base for a tonic or a martini.
Ice dilutes as it melts, so build the drink slightly stronger than you want it if you're a slow sipper.
Choosing Beans
Cold water extracts fewer acids, which mutes the bright, fruity notes that make a washed Ethiopian special. Medium roasts with chocolate, nut, and caramel character give you more for your money. Brazilian and Colombian coffees are reliable, affordable choices, and a natural-process bean adds a jammy sweetness that survives dilution well.
Use coffee roasted in the last four weeks. Cold brew is forgiving, but it can't rescue stale beans — it just makes their cardboard notes cold.
Troubleshooting
- Weak and watery — brew ratio too low, grind too coarse, or you diluted before tasting. Try 1:5 and 18 hours.
- Bitter or ashy — grind too fine, steeped too long, or you squeezed the filter bag.
- Sour and thin — under-extracted. Extend the steep by four hours or grind a touch finer.
- Cloudy and silty — skip straight to a paper filter for the second pass.
Takeaway
Cold brew concentrate is a weekly ritual that pays off every morning: brew at 1:5, steep 16–20 hours, filter twice, then dilute 1:2 in the glass. Weigh your coffee and water once, write down what you liked, and you'll have a house recipe dialled in within two batches.
