Ask Kate About Beer: How much caffeine is in coffee beers?

Illustration for article titled Ask Kate About Beer: How much caffeine is in coffee beers?
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Welcome to Ask Kate About Beer, in which The Takeout’s resident beer expert answers everything you’ve ever wanted to know about beer but were too drunk to ask. Have a question? Shoot it to


Kate, How much caffeine is in all of these coffee stouts? Sometimes I don’t notice the caffeine at all, but other times I’m up all night after having one. Is there any way to tell whether I should skip the barrel-aged nightcap because of caffeine-induced insomnia?

Cheers, Chad

Hey Chad,

Great question. In all my years drinking beer, I can’t recall ever seeing a label that listed a coffee beer’s caffeine content, or that even made mention of the fact that it contained caffeine. I can find information on a beer’s original gravity, final gravity, color via SRM scale, hop varietals, etc., but if I want to know whether it might keep me awake at night—no dice.

I reached out to a wide swath of breweries large and small that brew beers with coffee; nearly all said it wasn’t something they measure. Only two that I spoke to, Boston’s Harpoon Brewing and Kansas City’s Boulevard Brewing, could give me a precise caffeine content reading.

“Each 12-ounce serving of Dunkin’ Coffee Porter has only 2.7 mg of caffeine,” Harpoon’s CEO and cofounder Dan Kenary told me. “For us, we add the coffee strictly for the purpose of adding flavor to the beer and not for any reason that pertains to its caffeine content. We like coffee and we like Dunkin’ and we like how Dunkin’ coffee tastes in a porter.” A Boulevard spokesperson tells me the brewery’s new Steep Drop nitro coffee milk stout contains 7.5 mg per 12 ounces. For comparison, the USDA estimates a can of cola has roughly 29 mg of caffeine, and a cup of brewed coffee has 95 mg.

So why don’t other breweries provide this information? Caffeine can be a powerful stimulant, and some people actively avoid it. Moreover, not every coffee beer will have a comparable level of caffeine, depending on how the coffee is incorporated in the brewing process. Corey Blodgett, head brewer at Milwaukee’s Gathering Place Brewing, tells me caffeine levels in a coffee beer where brewers add coffee to the mash (steeping grains) will be lower than for a beer that blends cold brew into it after fermentation, for example. Beers that cold-infuse coffee could have significant caffeine levels since they’re mimicking the process of making cold brew. Blodgett says many brewers assume the caffeine content of a 12-ounce can or bottle of coffee beer is roughly the same as a cup of coffee. (Editor’s note: Blodgett followed up with me to clarify that this is likely an overestimate; his calculations show Gathering Place’s coffee beers likely have much less caffeine per serving than coffee.)

I’ll admit, I’m perplexed as to why breweries don’t measure this precisely—or at all. Research from the soft drink and coffee industries indicate that UV/visible spectrophotometers can be used to measure caffeine content in liquids. Spectrophotometers are a tool that even many small breweries possess; if they’re already using it to measure other variables, could it be used for caffeine too? (There is some evidence that liquids like sodas or, potentially, beer contain compounds that absorb light at the same wavelength as caffeine, rendering those readings less accurate. More research on using spectrophotometers to measure caffeine content of beer would be welcome.) Of course, it might take more consumer inquiries to make this happen. So if a beer’s caffeine content matters to you, ask breweries about it.


Kate Bernot is a freelance writer and a certified beer judge. She was previously managing editor at The Takeout.


Rory B. Bellows

Hi Kate! Chemist here. Please please PLEASE forgive the following and just consider it aimed at comment-readers if it’s stuff you already know or is too basic for you.

I read the paper you included from the group in Pakistan about UV measurement of caffeine. It’s a fine enough paper, but has some drawbacks that I think keep it from being used to definitively measure the caffeine content of either brewed coffee or beer.

I gather from the paper (and from other background reading) that caffeine is most absorptive in the high-UV range of wavelength, peaking around 270-275 nm. Unfortunately, this is the absorptive range of a LOT of similarly-structured compounds, many of which would be extracted under the same conditions/solvents as caffeine, and caffeine has such a broad peak that it’s effectively impossible to distinguish it from many others. Put another way, the UV spectrum would tell you how much stuff is in your sample that absorbs at 270nm, but it wouldn’t tell you how much of that is caffeine. This is of particular concern in something like beer or coffee, which — being natural products — have a TON of other chemicals in them.

The solution is to use a more advanced separatory technique than the one they used (which was akin to separating everything in the mix according to whether it chemically prefers to be dissolved in water or oil). HPLC (or High Performance Liquid Chromatography) is well-suited for this sort of thing. You load a sample onto a tube of sticky stuff and flow a solvent over it; different chemicals take different amounts of time to pass through the tube depending on how well they stick, and when they exit the tube they get measured by a spectrophotometer. I’ve personally measured caffeine in coffee this way in an undergraduate lab setting, and it works well. The downside is you need a trained chemist (or at least technician) and an expensive HPLC instrument, which is beyond the capacity of most breweries, I would think.

Here’s hoping that was interesting/informative!