Cold brew, iced coffee, and hot coffee all start from the same beans. What separates them is extraction: how hot the water is, how long the grounds sit in it, how fine or coarse the grind is, and how concentrated the result is before it reaches your cup. That's also where most of the popular claims about acidity and caffeine come from, and a couple of them don't hold up as cleanly as they're usually repeated.
How each one is actually made
Hot coffee covers drip, pour-over, French press, and espresso, all brewed and served at brewing temperature, typically 195 to 205°F (90.5 to 96°C) per the Specialty Coffee Association's Gold Cup Standard for filtered coffee.[1] Drip, pour-over, and French press extract over a few minutes; espresso forces that same hot water through the grounds under pressure in under a minute, a different mechanism with its own separate SCA definition.
Iced coffee, in its simplest form, is hot coffee that's been cooled and poured over ice. The problem is that melting ice dilutes it, so most recipes brew it meaningfully stronger to begin with: one equipment maker's guide puts it at roughly 1:10 to 1:12 coffee to water for iced, versus 1:15 for the same hot brew.[6]
Cold brew is a different process entirely: coarsely ground coffee steeps in room-temperature or cold water for hours rather than minutes, then gets filtered. Most recipes call for 12 to 24 hours, though research on extraction has found the actual chemistry mostly finishes well before that (more on this below). The result is a concentrate, usually diluted with water or milk before serving.
The acidity claim, checked against real measurements
The most common claim about cold brew is that it's dramatically less acidic than hot coffee: "up to 67% less acid" is the number that circulates online, almost always without a source.
A 2018 study from Thomas Jefferson University directly measured this. Researchers Niny Rao and Megan Fuller brewed six coffees from five origins (Brazil, two separate lots from Ethiopia, Colombia, Myanmar, and Mexico) both hot (6-minute French press) and cold (7-hour steep) at the same coffee-to-water ratio, then measured pH and titratable acidity for each. The pH values were close either way: hot brews ranged from 4.85 to 5.10, cold brews from 4.96 to 5.13. Hot brew actually had substantially more titratable acid by the time it was measured, not less, and generally showed higher antioxidant activity as well, which the researchers suggest may be linked to that same acid content.[2]
None of this means cold brew and hot coffee taste the same: most people still describe cold brew as smoother and less sharp. But that's a taste observation, not something the pH data above explains: the measured acid difference actually runs the other way (hot brew measured higher, not lower), so whatever makes cold brew taste smoother to most people isn't simply "it has less acid in it." If you find hot coffee rough on your stomach, cold brew's smoother taste may still suit you better, just not necessarily for the specific acidity reason usually given.
Caffeine: it depends more on brewing than on temperature
The other common claim is that cold brew always has more caffeine. This one has real support, but with a catch.
A 2017 study from the same Thomas Jefferson University team measured caffeine extraction directly, brewing the same coffee hot and cold at matched ratios across different grind sizes and roast levels. With a coarse grind, typical of cold brew, cold extraction pulled out meaningfully more caffeine than hot: 1,230 mg/L cold versus 970 mg/L hot for a medium roast, and 990 mg/L cold versus 840 mg/L hot for a dark roast. With a medium grind, the gap mostly disappeared. The same study also found that caffeine extraction largely levels off by around 7 hours of steeping, well short of the 10 to 24 hours typical recipes call for.[3]
So cold brew concentrate genuinely can carry more caffeine per volume than an equivalent hot brew, but what lands in your cup also depends on how much you dilute the concentrate, and how your iced coffee was brewed in the first place. Menu data from major chains illustrates the point: one widely cited comparison lists Starbucks cold brew at roughly 205 mg of caffeine per 16 oz, their hot brewed coffee at 210 to 360 mg depending on roast, and their iced coffee at around 165 mg.[4] In other words: cold brew tends to be strong, but "cold" alone doesn't guarantee more caffeine than a given cup of hot coffee: how it's brewed and diluted matters just as much.
A better way to make iced coffee
The weak point of basic iced coffee (brew hot, let it cool, pour over ice) is dilution and flavor drift while it sits. Specialty coffee shops mostly solve this with flash brewing: brewing hot coffee directly onto ice instead of brewing it first and chilling it after. The ice chills the coffee at the moment it's extracted, instead of after it has already started cooling and oxidizing on the counter, which keeps more of the bright, aromatic character that a slow cooldown tends to flatten out. One published specialty-roaster recipe for this: about 21g of coarse-ground coffee to 300g of hot water (roughly a 1:14 ratio, stronger than a typical hot brew), poured over ice that outweighs the water itself (around 350g, split between an initial catch vessel and a second vessel for the final chill-down).[5]
Which one should you actually make
If you want your usual cup, just colder, and you're not fussy about it losing a little brightness, cooling hot coffee over ice is fine; brewing it directly onto ice (flash brew) gets you a noticeably better version of the same idea for barely more effort. If you want a big batch that keeps in the fridge for up to two weeks and you don't mind the wait, cold brew is the better fit, and its smoother, lower-perceived-sharpness profile is real even if the pH number behind it isn't what people usually claim. If caffeine content specifically is what you're optimizing for, don't assume "cold" automatically means "more": check how it was actually brewed and how diluted your particular cup is.
Sources
Brewing figures and research findings adapted from the sources below. Sources checked October 2026. Cup Taste is not affiliated with or endorsed by the Specialty Coffee Association, Seattle Coffee Gear, Thomas Jefferson University, Springer Nature (Scientific Reports), Healthline, Starbucks, Ozone Coffee Roasters, or Ratio Coffee.
[1] Specialty Coffee Association Gold Cup Standard (water temperature), as summarized in "Achieving the Gold Cup Standard: Your Guide to Brewing Excellence," Seattle Coffee Gear. https://www.seattlecoffeegear.com/blogs/learning-center/achieving-the-gold-cup-standard-your-guide-to-brewing-excellence
[2] Rao NZ, Fuller M. Acidity and Antioxidant Activity of Cold Brew Coffee. Scientific Reports. 2018;8:16030. https://doi.org/10.1038/s41598-018-34392-w
[3] Fuller M, Rao NZ. The Effect of Time, Roasting Temperature, and Grind Size on Caffeine and Chlorogenic Acid Concentrations in Cold Brew Coffee. Scientific Reports. 2017;7:17979. https://doi.org/10.1038/s41598-017-18247-4
[4] Starbucks caffeine figures as compiled in "How Much Caffeine Is in Cold Brew Coffee?," Healthline. https://www.healthline.com/nutrition/cold-brew-caffeine
[5] Ozone Coffee Roasters. Flash Brew Coffee brew guide. https://ozonecoffee.co.uk/pages/brew-guide-flash-brew-coffee
[6] Ratio Coffee. "The Surprising Reason Your Iced Coffee Always Tastes Watery." https://ratiocoffee.com/blogs/coffee-guides/the-surprising-reason-your-iced-coffee-always-tastes-watery