Most root beer is caffeine free. The one you have to watch is regular Barq's, which carries 22mg of caffeine per 12 oz per Coca-Cola's official Barq's page. Mug, A&W, and Diet Barq's all sit at 0mg. So if someone hands you a root beer and asks whether it will keep them up, the honest answer is "probably not, unless it's a regular Barq's."
Why one root beer has caffeine and the rest do not
Root beer flavor does not come from a caffeine-bearing plant the way coffee, tea, or cola nut extract does. There is no botanical reason for a root beer to contain caffeine at all. That is why the category is overwhelmingly caffeine free. Barq's is the odd one out because it adds caffeine on purpose. The brand even built old marketing around it with the "Barq's has bite" line, and that bite is partly the added caffeine.
Here is the part that trips people up behind the bar: the caffeine only lives in regular Barq's. Diet Barq's and Barq's Zero Sugar are caffeine free. Coca-Cola lists the regular version at 22mg per 12 oz and flags the diet and zero sugar versions as caffeine free. So the "does root beer have caffeine" question does not even have one answer for a single brand. It depends on which Barq's can you are holding.
For scale, 22mg is modest. A 12 oz can of Coca-Cola runs about 34mg, and a standard cup of brewed coffee is closer to 90 to 100mg. Regular Barq's has less caffeine than a cola and a fraction of a coffee. It is not nothing, but it is not going to wire anyone the way an energy drink does.
Root beer caffeine by brand
| Root beer | Serving | Caffeine | Source |
|---|---|---|---|
| Barq's (regular) | 12 oz | 22 mg | Coca-Cola |
| Diet Barq's / Barq's Zero Sugar | 12 oz | 0 mg | Coca-Cola |
| Mug Root Beer | 12 oz | 0 mg | PepsiCo |
| A&W Root Beer | 12 oz | 0 mg | A&W (labeled "No Caffeine") |
PepsiCo's product facts page lists Mug Root Beer at 0mg of caffeine per container. A&W prints "No Caffeine" right on the can and across its retail listings, and that applies to regular, the 10 calorie version, and the zero sugar version. If you are stocking a fridge for someone avoiding caffeine, A&W and Mug are safe defaults and so is any Diet Barq's.
A quick barista tip when a customer asks: check the can, not your memory. Regular Barq's is the trap. Everything else in the standard American root beer lineup is caffeine free, but formulations change and store brands vary, so the printed label is the only source that is always current.
For context, the FDA cites 400mg of caffeine a day as an amount generally not associated with negative effects in healthy adults. How caffeine affects you depends on your own tolerance and health, so treat these numbers as information, not advice.
Barista Life runs on coffee people. Browse the Barista Life shop to support the site.
Related caffeine numbers
FAQ
Does A&W root beer have caffeine? No. A&W Root Beer is caffeine free across its regular, 10 calorie, and zero sugar versions, and the cans are labeled "No Caffeine."
Does Barq's root beer have caffeine? Regular Barq's has 22mg of caffeine per 12 oz per Coca-Cola. Diet Barq's and Barq's Zero Sugar are caffeine free.
Which root beers are caffeine free? Mug, A&W, and Diet Barq's or Barq's Zero Sugar all have 0mg. The main exception in the category is regular Barq's.