Cold Brew vs Iced Coffee: What Actually Makes Them Different

Iced coffee is brewed hot and then cooled. Cold brew is never heated at all: coarse grounds steep in cold or room-temperature water for 12 to 24 hours, then get filtered. Everything else, the taste, the caffeine, the price, follows from that one difference.

Two things you have probably read about cold brew are not well supported by the evidence, and we go through both below with the actual studies.

Side by side

How each one is made

Cold brew

Coarse grounds go into cold water at a strong ratio, often around 1:8, and sit for 12 to 24 hours in the fridge or at room temperature. The result is filtered and usually kept as a concentrate, then diluted with water, milk or ice when you serve it. Because no heat is involved, extraction is slow, which is why it needs so long.

Iced coffee

Iced coffee is just coffee. It is brewed hot by any normal method, drip machine, pour-over, drip bag, French press, then chilled or poured over ice. It takes minutes, not a day.

The catch is dilution. Melting ice waters the coffee down, which is why iced coffee often tastes thin. Two fixes: brew it stronger than usual, or use the Japanese method below.

Japanese iced coffee, the third option nobody mentions

Also called flash brew. You brew hot directly onto ice, replacing part of your brewing water with the equivalent weight of ice in the vessel below. The coffee is chilled the instant it is made, so it keeps the bright, aromatic character that hot brewing produces, but never sits around going stale or watery.

It takes three minutes instead of a day, and it is the method we use for our own iced coffee at home guide.

Caffeine: the numbers, and why they are confusing

Most articles quote caffeine figures without saying what size cup they are talking about, which makes the comparison meaningless. Here are published figures from one brand, at one size, so they are actually comparable. These are Starbucks' own published values for a 16 oz (473 ml) grande.

So yes, cold brew has more caffeine than iced coffee. But look at the last row: ordinary hot brewed coffee has considerably more caffeine than cold brew in the same size cup. That should tell you the cold water is not what is doing the work.

Why cold brew is stronger

It is the recipe, not the temperature. Cold brew is made at a much higher coffee-to-water ratio and steeped for hours, so more coffee ends up in the same volume of liquid.

Research backs this up. Fuller and Rao, publishing in Scientific Reports in 2017, compared hot and cold brewing at the same coffee-to-water ratio and found the difference in caffeine was not statistically significant at a medium grind. Hot water is not a worse solvent for caffeine; hot brewing is simply limited by how briefly the water is in contact with the coffee.

The practical takeaway: how strong your coffee is depends mostly on how much coffee you used, not how hot the water was. Our coffee ratio guide covers how to control that.

Acidity: what the research actually says

You will see "cold brew is up to 67% less acidic" repeated everywhere. We went looking for the study behind it and could not find one. It appears to come from marketing copy rather than research.

What has actually been measured is more modest. In a 2018 study in Scientific Reports, Rao and Fuller compared hot and cold brews of six light-roast coffees. They found:

• pH was essentially the same. Every sample, hot or cold, landed between 4.85 and 5.13. The authors concluded that changing the water temperature did not produce distinguishable pH values.
• Titratable acidity was lower in cold brew. This is a different measure, roughly how much acid is present in total, and here cold brew was consistently lower. This is the real basis for the smoother taste.
• Hot brew had higher antioxidant activity, which the researchers flagged as a possible trade-off.

So cold brew is genuinely gentler tasting, and lower in total acids. But it is not dramatically less acidic on the pH scale, and the university that ran the study specifically cautioned against treating cold brew as a cure for stomach trouble. If coffee upsets your stomach, cold brew may help, but do not count on it, and talk to a doctor if it is a persistent problem.

Calories: no real difference

Black cold brew and black iced coffee are both essentially calorie-free, under about 5 calories a cup. Any meaningful calorie difference comes from what goes in afterwards: milk, cream, sweetened condensed milk, flavoured syrups.

One thing worth knowing in a coffee shop: iced coffee is frequently sweetened by default in North America, while cold brew is more often served black. If you are watching sugar, ask.

Which is healthier?

For most people, neither has a meaningful edge. Both are coffee. The differences that matter are the ones you add.

If you find hot coffee harsh, cold brew's lower total acidity may sit better with you. If antioxidant content matters to you, the 2018 study suggests hot brewing has a slight advantage. Either way, the sugar and cream you put in will affect your health far more than the brewing temperature did.

The downsides of cold brew

It is not all upside, which most articles skip.

• It takes a day. No cold brew is happening if you want coffee in ten minutes.
• It uses a lot of coffee. A 1:8 concentrate uses roughly twice the beans per litre of finished drink.
• It is easy to over-caffeinate. Concentrate that has not been diluted properly is very strong, and it does not taste as strong as it is.
• It flattens the coffee's character. The floral and fruity notes that make a good Ethiopian coffee interesting are largely aromatic, and cold water pulls out fewer of them. Cold brew tends toward chocolate and nuts regardless of the bean.
• It costs more in shops, because of the time and the amount of coffee involved.

Should you put milk in cold brew?

Entirely your call. Cold brew is smooth and low in bitterness, so plenty of people drink it black who would not drink hot coffee black. Milk or oat milk works well with its chocolatey character, and cold brew's strength means a splash will not wash it out the way it can with iced coffee.

If you are using concentrate, milk can do the diluting job that water would otherwise do.

Which should you actually make at home?

If you want it now, make iced coffee, ideally by the Japanese method so it does not end up watery. If you want a batch to last the week and you like a smooth, chocolatey, low-bitterness cup, make cold brew on a Sunday night.

For a single cold cup with no planning and no equipment, a drip bag is the shortcut. Brew it straight onto ice in the mug for flash-brewed iced coffee in about three minutes.

KNDZ drip bags are 100% Arabica specialty-grade beans from Ethiopia and Colombia, roasted in micro-batches in Toronto by a Certified Q Grader, pre-measured and sealed one cup at a time. The Everyday Medium Roast makes a bright, clean iced coffee; Simply Dark Roast gives you the fuller, low-acid character people usually go to cold brew for.

Shop KNDZ drip bag coffee

Frequently asked questions

Is cold brew stronger than iced coffee?

Usually yes. Starbucks publishes 205 mg of caffeine for a 16 oz Cold Brew against 185 mg for a 16 oz Iced Coffee. The reason is the recipe rather than the temperature: cold brew uses far more coffee per unit of water and steeps for many hours. Notably, hot brewed coffee at the same size has more caffeine than either.

What is healthier, iced coffee or cold brew?

There is no meaningful health gap between them when both are black. Cold brew has lower total titratable acidity, which can feel gentler, but research found the pH of hot and cold brews is essentially the same, and hot brew showed higher antioxidant activity. What you add, milk, cream and syrup, matters far more than the brewing method.

What are the disadvantages of cold brew coffee?

It takes 12 to 24 hours, uses roughly twice as much coffee, costs more in shops, and is easy to over-caffeinate if the concentrate is not diluted properly. It also mutes the floral and fruity aromatics of lighter coffees, so most cold brew tastes chocolatey regardless of the bean.

Are you supposed to put milk in cold brew?

There is no rule. Cold brew is smooth enough that many people drink it black, but milk or oat milk suits its chocolatey character well, and if you are working from concentrate, milk can do the diluting instead of water.

Is cold brew less acidic than regular coffee?

Somewhat, but less than the marketing suggests. A 2018 study in Scientific Reports found hot and cold brews of the same coffees all sat between pH 4.85 and 5.13, with no distinguishable difference by temperature. Cold brew did have lower titratable acidity, which is why it tastes smoother.

How long does cold brew last in the fridge?

Homemade cold brew is generally good for about a week refrigerated, and concentrate keeps a little longer than diluted cold brew. Iced coffee is best drunk the day it is made.

Related guides

• How to make iced coffee at home Three easy methods, including the Japanese flash-brew.
• Pour-over coffee ratio How much coffee to use, and why it controls strength.
• Dark roast vs medium roast How roast level changes taste, caffeine and acidity.