Only Barq's root beer carries caffeine here: 22mg per 12 oz can. A&W Root Beer and Mug Root Beer are caffeine-free, so the answer to which of the three keeps you up is not close.
Barq's root beer vs A&W Root Beer vs Mug Root Beer: the numbers
| Barq's root beer | A&W Root Beer | Mug Root Beer | |
|---|---|---|---|
| Caffeine per serving | 22mg per 12 oz can | 0mg per 12 oz can | 0mg per 12 oz can |
| Caffeine per fl oz | 1.8mg | 0mg | 0mg |
| Servings to reach 400mg (FDA context) | 18.2 | n/a (caffeine-free) | n/a (caffeine-free) |
Sources: Barq's root beer is 22mg per 12 oz can per Caffeine Informer (source), and the figure is carried in our Barq's root beer guide; A&W Root Beer is 0mg per 12 oz can per Caffeine Informer (source), and the figure is carried in our A&W Root Beer guide; Mug Root Beer is 0mg per 12 oz can per Caffeine Informer (source), and the figure is carried in our Mug Root Beer guide.
Why one of these has caffeine and the others do not
None of the three gets caffeine from the recipe by accident. Caffeine is an added ingredient in this category, so a brand either puts it in or it does not, and the label says which. Barq's root beer lists 22mg per 12 oz can; A&W Root Beer and Mug Root Beer list none. Flavors and zero-sugar versions of the same brand can differ, so read the panel rather than assuming the line is consistent.
The three head-to-head pages
Each pairing has its own page with the full math:
Which one should you pick?
If the goal is avoiding caffeine, A&W Root Beer and Mug Root Beer do that at 0mg. If you want the caffeine, Barq's root beer is the only real option of the three at 22mg per 12 oz can. Check the label anyway when a brand runs limited flavors, since caffeine sometimes appears in one variant of a caffeine-free line.
For context, the FDA cites 400mg of caffeine a day as an amount generally not associated with negative effects in healthy adults. Tolerance and health vary, so treat these numbers as information, not advice.
Related reading
- The verified caffeine database
- Every drink compared: the comparisons index
- Compare any two of 120+ drinks
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Gear from this guide
FAQ
Which has the most caffeine, Barq's root beer, A&W Root Beer or Mug Root Beer? Barq's root beer, at 22mg per 12 oz can. A&W Root Beer has 0mg per 12 oz can and Mug Root Beer has 0mg per 12 oz can.
Which of the three is strongest per ounce? Barq's root beer, at about 1.8mg per fluid ounce, ahead of A&W Root Beer at 0mg and Mug Root Beer at 0mg.
How many Barq's root beer servings reach the FDA 400mg reference? About 18.2 of them, at 12 oz can each. The FDA cites 400mg a day as an amount generally not associated with negative effects in healthy adults. This is information, not advice.
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