How to Make Cold Brew in a Mason Jar (No Gear Needed)

To make cold brew in a mason jar, stir coarsely ground coffee into cold or room-temperature water at about 1 part coffee to 4 parts water by weight, close the lid, steep for around 12 hours, then strain it through a sieve lined with cheesecloth or a paper filter. A quart jar, a sieve and a second container are all the gear it takes. The National Coffee Association (NCA) lists a jar as a perfectly good container: “anything in your kitchen that can hold coffee and water will be fine” (NCA cold brew guide).

Below: the amounts for one jar, the steps, how long the result keeps, how to serve it, and the mistakes that make a batch weak or bitter. Daily Home Coffee does not test products; the figures here come from the named sources or from the arithmetic of the recipe.

What You’ll Need to Make Cold Brew in a Mason Jar

The NCA’s quick numbers for cold brew are a coffee-to-water ratio of “1 gram of coffee to 4-5 grams of water (1:4 to 1:5)”, room temperature or cooler water, and “an approximate 12 hours of contact between coffee and water”. Everything below is built on those three figures.

Ingredients

• Coarsely ground coffee: 150 g
• Cold filtered water: 600 ml (600 g, since a millilitre of water weighs about a gram)

150 g of coffee to 600 g of water is exactly 1:4, the stronger end of the NCA range, which gives a concentrate to dilute when you serve it. For a slightly lighter batch at 1:5, keep the 600 ml of water and use 120 g of coffee. A kitchen scale is the easiest way to hit these numbers; the NCA notes that weighing coffee and water “will help you make more consistent cold brew coffee”, and it lets you repeat a batch you liked.

Gear

• A quart-sized mason jar with a lid, or any large jar
• A fine-mesh strainer or sieve
• Cheesecloth or a paper coffee filter to line the sieve
• A second jar or pitcher with a lid, for the finished cold brew
• A kitchen scale, if you have one

Leave some space at the top of the jar. Dry grounds take up room before they absorb water, so if the coffee and water do not fit comfortably, scale both down by the same proportion: 100 g of coffee to 400 ml of water is still 1:4.

Step-by-Step: How to Make Cold Brew in a Mason Jar

1. Grind Your Coffee Coarsely

The NCA’s hands-on method starts with coarsely ground coffee and advises grinding “as close as possible to when you brew”. A coarse grind is also what lets a sieve and cheesecloth hold the grounds back when you strain. If you buy pre-ground coffee, look for a bag labelled coarse or for cold brew, or ask the roaster to grind it coarse.

2. Combine Coffee and Water in Your Mason Jar

Put the 150 g of grounds in the jar, then add the 600 ml of water gradually and stir gently, “making sure all the coffee grounds are moistened”, as the NCA puts it. Some grounds float at first; a second gentle stir after a few minutes wets them.

The NCA recommends filtered water if possible and says to avoid distilled or softened water. Water is most of what ends up in the jar, so its taste carries into the coffee.

3. Cover and Steep

Close the lid and let the jar steep. The NCA’s instruction is to “let the coffee sit and steep in the refrigerator or at room temperature for 12 hours, or overnight”, and it adds: “Don’t rush this step—time is everything for cold brew coffee!”

Where it steeps	Steep time	What it means for storage
Refrigerator	About 12 hours, or overnight	Covered by the seven-day ceiling below
Room temperature	About 12 hours, or overnight	No source cited here gives a keeping time; steep in the fridge if you plan to store it

If you plan to keep the jar for several days, steep it in the fridge. That is the case the storage guidance below covers.

4. Strain Your Cold Brew

Set the sieve over the second jar or pitcher, line it with cheesecloth or a paper filter, and pour the cold brew through slowly. The NCA says to “strain a second time if needed”: the first pass removes most of the grounds and a second pass catches finer sediment.

If you use a paper filter, rinse it with water first. The NCA notes that paper filters can leave “an unpleasant, papery taste” and that rinsing any paper filter before brewing is an easy fix. Paper also holds back more of the coffee’s oils than cloth, which the NCA says can give “a cleaner, lighter taste”.

5. Store It in the Fridge

Move the strained concentrate to a clean jar with a lid and refrigerate it straight away. Wisconsin’s agriculture department treats cold brew made without a heat step as a time/temperature control for safety food that needs refrigeration. Its retail guidance, written for cafés and shops, requires no HACCP plan or variance when cold brew is brewed, held and served at 41 °F or below and date-marked for no more than seven days from production (Wisconsin DATCP cold brew fact sheet). This site applies the same seven days at home as a conservative ceiling for a jar steeped and kept in the fridge, counted from the day you brewed it. Write the date on the lid. The cold brew shelf life guide covers the reasoning in full.

When you are done, wash the jar, sieve and any cloth. The NCA warns that coffee grounds and oil left behind “can make your next cup taste bitter”.

What to Expect from the Taste

The NCA says brewing without heat over a longer time gives “a smoother, more mellow cup” and that cold brew “offers a less bitter, smoother taste” than iced coffee. The flavours you notice still depend on the beans you choose.

Cold brew is often described as gentler on the stomach. The evidence is narrower than that. Rao and Fuller compared cold and hot brews made from the same light-roast coffees: the pH of the two was comparable, ranging from 4.85 to 5.13, and the hot brews had higher total titratable acidity (Rao & Fuller, 2018). That study measured the coffee, not anyone’s digestion, and this is not medical advice.

How to Serve Your Mason Jar Cold Brew

A 1:4 batch is a concentrate, which the NCA describes as “designed to be diluted with water or enjoyed with ice, even as it melts”. Dilute each glass as you pour it, not the whole jar. One part concentrate to two parts water is a sensible start, with one to one for a stronger glass and one to three for a lighter one; the cold brew dilution guide works through each ratio.

• Iced: fill a glass with ice, add concentrate and cold water. Ice melt thins the drink further, so use a little less water if the glass is packed with ice.
• With milk: replace some or all of the water with dairy or plant milk.
• Sweetened: stir in simple syrup or a flavoured syrup, and count it as part of the liquid you add.
• Hot: the NCA notes that cold brew “can be served hot or over ice”. Dilute the concentrate with hot water in a heat-safe mug.

Mix milk drinks to order and put the jar back in the fridge. The USDA’s general rule for perishable food is that it should not sit out of refrigeration for more than two hours, or one hour above 90 °F (USDA FSIS “Danger Zone”). Applying it to the jar of concentrate is this site’s reasoning, not a cold-brew-specific USDA rule.

Common Mistakes When Making Cold Brew (And How to Avoid Them)

Using the Wrong Grind Size

The NCA method calls for coarsely ground coffee. Finer grounds are harder to hold back with a sieve and cloth, so expect more sediment in the jar.

Cutting the Steep Short

The NCA’s figure is about 12 hours of contact, and its instruction is not to rush it. If a batch tastes thin, check the steep time before changing anything else.

Guessing the Amounts

Measuring by the cup leaves the ratio to guesswork. Weigh the coffee and the water, as the NCA suggests, and change one thing at a time so you know what made the difference.

Using Low-Quality or Stale Coffee

Cold brew is forgiving, but it cannot add flavour the beans no longer have. The NCA’s three basics are choosing beans you like, grinding them as close as possible to brewing, and using filtered water. If a batch tastes flat with good water and a full steep, try fresher beans.

Leaving the Jar on the Counter

Once strained, the concentrate belongs in the fridge. A jar left out after a room-temperature steep is outside the seven-day guidance above.

Frequently Asked Questions

Can I use regular ground coffee for cold brew?

Yes, but check the grind. The NCA method uses coarsely ground coffee, so look for a bag labelled coarse or for cold brew. If your coffee is finer, expect more sediment and strain twice.

How long does cold brew last in the fridge?

For a jar steeped and kept in the fridge, treat seven days from the day it was brewed as the ceiling. That figure comes from Wisconsin’s retail guidance applied at home as a conservative limit. None of the sources cited here gives a keeping time for a batch steeped at room temperature. If it smells or tastes off before then, pour it out.

What’s the difference between cold brew and iced coffee?

The NCA’s definition: “Iced coffee is coffee that has been brewed hot using a standard method, then cooled down to serve. Cold brew is brewed with room temperature or cooler water and can be served hot or over ice.”

Can I heat up cold brew?

Yes. Dilute the concentrate with hot water rather than cold. The NCA notes that cold brew can be served hot.

Why does my cold brew taste weak?

There are three usual causes: too little coffee for the water, too short a steep, or too much water or ice when serving. Weigh the next batch at 1:4, steep for about 12 hours, and dilute one glass at 1:2 before going further.

Your Next Batch

Weigh 150 g of coarse grounds and 600 ml of filtered water into the jar, stir, cover and refrigerate for about 12 hours. Strain through a lined sieve, a second time if needed, date the lid, and finish the jar within seven days. Pour one glass at 1:2, taste it, and adjust from there.