# How to Make Cold Brew Coffee

> A 1:8 cold brew recipe you can pour straight over ice, with grind size, steep times, filtering technique and a fix for every common fault.

Topic: Cold Brew & Iced  
Published: 2026-08-29T09:05:00-04:00  
Updated: 2026-08-29T09:05:00-04:00  
Author: Mical Robert, Editor (https://trysix.online/author/mical-robert)  
Canonical: https://trysix.online/how-to-make-cold-brew-coffee

## The short answer

Steep coarsely ground coffee in cold water at 1:8 by weight — 125 g to 1 litre — for 16 hours at room temperature or up to 24 in the fridge, then strain. No heat at any stage. It keeps about a week.

## Key takeaways

- 1:8 by weight gives ready-to-drink cold brew. 1:5 gives concentrate that needs diluting.
- Coarse grind, always. Fine grounds over-extract across a 16-hour steep and clog the filter.
- Room temperature is faster than the fridge. 16 hours on the counter is roughly 20–24 in the cold.
- Strain twice and never squeeze the bed — pressing forces bitter liquid through the fines.

Cold brew is the rare coffee method where patience does all the work. There is no technique to master, no timing to hit, and almost nothing to get wrong — you put coffee in water, walk away overnight, and strain it in the morning. The two things people do get wrong are both easy to avoid.

## What cold brew actually is

Cold brew is coffee extracted without heat. Grounds sit in cold or room-temperature water for the better part of a day, and time does the work that temperature does in a drip machine. That single change alters what ends up in the cup: cold water is a poorer solvent for many of the acids and aromatic compounds that hot water pulls readily, so the result reads as rounder, sweeter and less bright.

It is not the same drink as [iced coffee](https://trysix.online/cold-brew-vs-iced-coffee), which is brewed hot and then chilled. And it is not automatically stronger, though it often is as sold — that depends entirely on the ratio, which is what this recipe pins down.

> **The ratio decides everything** — 1:8 by weight — 125 g of coffee, 1 litre of water — is drinkable straight from the bottle. 1:5 is concentrate. Everything else on this page is technique; this is the recipe.

## What you need

- 125 g whole beans, ground coarse. A medium roast is the easiest starting point; see [the best coffee for cold brew](https://trysix.online/best-coffee-for-beginners) if you are buying specifically for this.
- 1 litre of cold water. If your tap water tastes of chlorine, filter it — you are about to concentrate that flavour over 16 hours.
- A 1.5-litre jar, jug or French press
- A fine mesh sieve, and a paper filter, cloth or nut-milk bag for the second strain
- A kitchen scale. Volume measures are the single most common cause of a weak batch.

> **Why a scale, specifically** — Ground coffee density varies with roast level and grind size. A level tablespoon of coarse-ground light roast weighs noticeably more than the same spoon of oily dark roast, so scoop-based recipes drift by 20 percent or more between bags. Weighing removes that variable permanently.

### The method

1. **Grind coarse** — Coarse means visibly chunky — the texture of raw sugar or coarse sea salt, not sand and certainly not powder. Grind size sets how much surface area the water can reach, and across 16 hours a fine grind extracts far past the point where it tastes good. Our [grinding guide](https://trysix.online/how-to-grind-coffee-beans) shows the size against other brew methods.
2. **Wet everything** — Add the grounds to the jar, pour on the litre of water, and stir until no dry clumps remain floating. Dry pockets never extract, and they are the reason an otherwise correct batch tastes weak.
3. **Steep** — Cover and leave 16 hours at room temperature, or 20 to 24 hours in the fridge. Extraction rate rises with temperature, so the counter is faster; the fridge is slower but slightly cleaner-tasting and safer in a warm kitchen.
4. **Strain coarse first** — Pour through the mesh sieve into a second container to remove the bulk of the grounds. If you brewed in a French press, press the plunger down slowly and stop before it compresses the bed.
5. **Strain fine second** — Pass the liquid through a paper filter, cloth or nut-milk bag. This catches the fines that make cold brew taste silty. Let it drip; do not squeeze or wring the filter, which forces over-extracted bitter liquid through.
6. **Bottle and date** — Into a sealed bottle in the fridge. Ready-to-drink cold brew is at its best within about five days and drinkable for about a week; after that it flattens noticeably.

## Steep time, and why longer is not stronger

Extraction is fast at first and slows sharply. A 2017 study in Scientific Reports measured caffeine and chlorogenic acid across steep times, temperatures and grind sizes, and found that once the readily soluble material is out, further hours add very little of what you want and a fair amount of what you do not.

**Figure: What each stage of the steep contributes**

| Item | Value |
| --- | --- |
| Grassy, sour, obviously unfinished | 6h |
| Drinkable but thin | 12h |
| Balanced — the target | 16h |
| Full-bodied; fridge equivalent | 24h |
| Woody, papery, over-steeped | 36h |

_Room-temperature steep, coarse grind. The useful window is broad; the failure modes sit at both ends._

If your cold brew is too weak, the fix is more coffee, not more hours. Going from 1:8 to 1:6 changes the drink; going from 16 hours to 30 mostly adds wood.

## Ratios at a glance

**Common cold brew ratios by weight, and what each is for.**

| Ratio | Coffee per litre | Result | Use it for |
| --- | --- | --- | --- |
| 1:5 | 200 g | Concentrate | [Diluting to order](https://trysix.online/how-to-make-cold-brew-concentrate); milk drinks |
| 1:6 | 165 g | Strong ready-to-drink | Pouring over a full glass of ice |
| 1:8 | 125 g | Ready-to-drink | Drinking straight from the bottle |
| 1:12 | 83 g | Light and tea-like | All-day sipping; light roasts |
| 1:16 | 62 g | Too weak for cold brew | This is a drip ratio, not a cold one |

That last row is worth dwelling on. A 1:16 ratio makes perfectly good hot coffee, because hot water extracts far more efficiently. Cold water does not, so a cold steep at drip ratios tastes hollow. Cold brew needs more coffee to reach the same perceived strength — which is exactly why it costs more per glass than a drip cup.

## Fixing a bad batch

**Symptoms and what actually causes them.**

| Symptom | Cause | Fix |
| --- | --- | --- |
| Bitter and drying | Grind too fine, or the filter was squeezed | Coarsen the grind; let it drain unaided |
| Sour and hollow | Under-steeped or ratio too weak | 16 h minimum; move to 1:6 |
| Gritty, silty mouthfeel | One strain only | Second strain through paper or cloth |
| Flat and cardboard-like | Stale beans, or brewed over a week ago | Check the roast date; drink within 5 days |
| Tastes of chlorine | Tap water | Filter the water before brewing |
| Weak despite 1:8 | Measured by volume, not weight | Weigh it — scoops vary by 20 percent or more |

## Serving it

1. Over ice, straight from the bottle. This is what 1:8 is for.
2. Half cold brew, half milk, over ice — closer to a coffee-flavoured milk than a latte, because 1:8 is not strong enough to stand up to dairy. For milk drinks, brew [concentrate](https://trysix.online/how-to-make-cold-brew-concentrate) instead.
3. Hot: pour 150 ml of cold brew into a mug and top with 50 ml of boiling water. It will taste different from a hot-brewed cup — flatter and sweeter — because the aromatic compounds were never extracted in the first place.
4. With a pinch of salt, if it reads as bitter. Salt suppresses bitterness perception more effectively than sugar does.

> Cold brew coffee samples were measurably less acidic than their hot-brewed counterparts at equivalent roast levels.
>
> — Rao & Fuller, Scientific Reports (2018)

That measured drop in acidity is the honest core of the health claims made for cold brew — and it is narrower than the marketing suggests. [Whether cold brew is actually healthier](https://trysix.online/is-cold-brew-coffee-healthy) goes through what has and has not been shown. If you want to know how the caffeine compares, see [is cold brew stronger](https://trysix.online/is-cold-brew-stronger).

## Frequently asked questions

### Can I use pre-ground coffee for cold brew?

Yes, though supermarket pre-ground is cut for drip machines and is finer than ideal. Shorten the steep to about 12 hours, strain twice, and accept more sediment. Buying coarse-ground or grinding your own gives a cleaner result.

### Does cold brew need to be refrigerated while steeping?

Not necessarily. Room-temperature steeping is standard and extracts faster. In a warm kitchen — above about 25°C — the fridge is the safer choice, and you extend the steep to 20–24 hours to compensate for the slower extraction.

### How long does cold brew last?

Sealed in the fridge, undiluted cold brew is at its best for about five days and drinkable for around a week. It does not spoil dramatically; it flattens, losing sweetness and picking up a dull, cardboard note.

### Can I reuse the grounds for a second batch?

You can, but the second batch will be very weak — most of the soluble material came out the first time. The grounds are more useful in a compost heap than in a second jar.

## Sources

- [The Effect of Time, Roasting Temperature, and Grind Size on Caffeine and Chlorogenic Acid Concentrations in Cold Brew Coffee](https://doi.org/10.1038/s41598-017-18247-4) — Scientific Reports (2017) (DOI 10.1038/s41598-017-18247-4). Supports the finding that cold brew extraction slows sharply after the early hours of the steep.
- [Acidity and Antioxidant Activity of Cold Brew Coffee](https://doi.org/10.1038/s41598-018-34392-w) — Scientific Reports (2018) (DOI 10.1038/s41598-018-34392-w). Supports the measured claim that cold brew is less acidic than hot-brewed coffee at matched roast levels.
- [How to Brew Coffee](https://www.ncausa.org/About-Coffee/How-to-Brew-Coffee) — National Coffee Association USA. Supports the 1:16 hot-brew baseline used to explain why cold brew needs a stronger ratio.

## Related articles

- https://trysix.online/how-to-make-cold-brew-concentrate
- https://trysix.online/cold-brew-vs-iced-coffee
- https://trysix.online/is-cold-brew-stronger
- https://trysix.online/how-to-grind-coffee-beans

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