ZOA has more caffeine than Diet Barq's root beer: 160mg vs 0mg in the same 12 oz can. That is a 160mg gap, and since the cans match, the per-serving number is the whole story.
These are different categories of drink, which changes how the caffeine arrives. Energy drinks and sodas list an exact number because caffeine is a measured additive; brewed drinks vary with the beans and the brew, so their figures are compiled averages. The numbers here are the standard published values for each.
ZOA vs Diet Barq's root beer: the numbers
| ZOA | Diet Barq's root beer | |
|---|---|---|
| Caffeine per serving | 160mg per 12 oz can | 0mg per 12 oz can |
| Caffeine per fl oz | 13.3mg | 0.0mg |
| Servings to reach 400mg (FDA context) | 2.5 | n/a (caffeine-free) |
Sources: ZOA's figure is verified in our ZOA caffeine guide against ZOA FAQ (source); Diet Barq's root beer's figure is verified in our Diet Barq's root beer guide against Caffeine Informer / Coca-Cola brand data (source).
The concentration gap is the striking part: ZOA packs roughly 1333 times the caffeine per ounce. Sipping speed matters at that density; a 12 oz can finished in minutes hits differently than the same milligrams spread over a slow cup.
Which one should you pick?
Pick Diet Barq's root beer when you want the lighter dose or a slower ramp, and ZOA when you actually need the bigger hit and know your tolerance. If you are stacking either with other caffeinated drinks through the day, run the math against the 400mg reference rather than guessing.
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
- ZOA: the full caffeine guide
- Diet Barq's root beer: the full caffeine guide
- The verified caffeine database
FAQ
Does ZOA or Diet Barq's root beer have more caffeine? ZOA: 160mg per 12 oz can versus 0mg per 12 oz can for Diet Barq's root beer.
Which is stronger per ounce? ZOA, at about 13.3mg per fluid ounce versus 0.0mg for Diet Barq's root beer.
Comparing caffeine? The caffeine comparison tool puts hundreds of drinks side by side, and the caffeine curfew calculator can check your cutoff time for tonight.